LIEN QUAN VA DIEU HOA CHUYEN HOA
Hinh 6.8. Operon tryptophan d trang thai kim ham
6. Neuva gidi thich dtfdc nguyen nhan gay ro'i loan trao do'i ntfdc va cac chat vo cd,hau qua va
1.4. Stf phan bo'ntfdc va cac cha't dien giai trong cd the
^ Ntfdc la thanh phln chii ydu cua dich cd thd, chidm khoang 45 -75% tdng trong ltfdng cd
the. Ntfdc va cac chat dien giai dtfdc phan pho'i dhai khu vtfc chii yeu:
♦> Khu vtfc noi bao (trong td bao): chtfa khoang 2/3 tdng Itfdng ntfdc trong cd thd (63%)
va nhieu ion K+, Mg2+, HP042", protein ...
♦ Khu vtfc ngoai bao (ngoai td bao): chtfa khoang 1/3 tong Itfdng ntfdc trog cd the (37%),
gdmcd:
- dich gian bao hay dich ke (giffa cac tdbao).
- huye't ttfdng (trong mach mau) - bach huye't (trong mach bach huyet)
Khu vtfc ngoai bao con cd dich truydn te bao (transcellular) nhtf dich nao tuy, dich thiiy
va dich thuy tinh the ciia mat, hoat dich ciia khdp xtfdng ...
Dich gian bao va huye't ttfdng chiem ty le ldn ciia dich ngoai bao.
Dich ngoai bao chtfa nhieu ion Na+, CI", HC03".
1.5. Stf vanchuydn ntfdc trong cd the
Sau khi dtfdc hap thu ttf dng tieu hda, ntfdc dtfdc van chuydn den cac td chtfc cua cd thd
mang cac cha't dinh dtfdng de'n di td bao stf dung. Ttf huydt ttfdng, ntfdc qua thanh mach dd vao' dich gian bao, ttf dich gian bao ntfdc lai tham qua mang tdbao vao khu vtfc ben trong tdbao.
Dong thdi cQng cd qu<i trinh van chuyen ntfdc ngtfdc trd lai: ttf te bao vao dich gian bao roi vao huydt ttfdng. Ttf huydt ttfdng ntfdc dtfdc dtfa ddn cac cd quan bai tidt cung vdi cac cha't
can ba ciia te bao dd dtfdc dao thai ra ngoai.
Nhd stf van chuyen nay, ntfdc trong cd the luon luon dtfdc ddi mdi (6% tdng ltfdng ntfdc
trong cd the dtfdc ddi mdi trong 24 gid).
1.5.1. Cac ye'u ta'anh htfdrng
Ntfdc van chuyen dtfdc trong cd the la nhd mot sd yeu td quyet dinh dtfa vao stf chenh
lech ap sua't giffa cac td chtfc.
1.5.1.1. Ap sua't tmfmtha'u
Laltfc cd tac dung giff ntfdc va keo ntfdc vao phan dich ma nd chiem giff, day la yeu td cd ban nhat quye't dinh stf van chuyen va phan bo dich trong cac khu vtfc.
Ap sua't tham thau d khu vtfc nao cang cao thi ntfdc se dtfdc van chuydn vao do cang
nhieu va ngtfdc lai.
Ap sua't tham thau do cac ye'u td hda tan trong ntfdc dcac dich tao nen, gdm cd:
- Cac cha't dien giai: la yeu tdquan trong tao nen ap ltfc tham thau cua cac dich, do do dong vai tro quye't dinh stf phan bd va van chuyen ntfdc trong cd the. Vi du: dich ngoai bao cd
nhieu Na+, CI"; dich noi bao cd nhieu K+, HP04".
- Cac hdp cha't hffucdco phan tuf Itfdng nho (glucose, ure, acid amin...):
Cd the dtfdc van chuyen de dang qua mang tdbao va thanh mach nen ndng do tron<* hau het cac dich ciia cd the va ap ltfc tham thau do chiing tao ra gan gidng nhau. Do dd, cac chat nay
chi tham gia dieu chinh ltfdng ntfdc toan phan ciia cd the chtf khong gay nen stf van chuyen ntfdc giffa cac khu vtfc vdi nhau.
- Cac hdp cha't htfu cd co phan tuf ltfdng ldn (chii yeu la protein)
Vi ham ltfdng protein trong cac dich cd the ra't khac nhau nen phan ap ltfc tham thau do nd tao nen (ap sua't keo) d cac khu vtfc ntfdc khac nhau ciia cd the cung khac nhau.
Vi du : - Protein trong huye't ttfdng tao ap ltfc tham thau la 25mm Hg.
- Protein ciia dich ngoai te bao tao ap ltfc tham thau la 10mm Hg.
- Protein ciia dich trong te bao tao ap ltfc tham thau rat ldn vi cd ndng do cao gap 3-5 Ian protein trong huye't ttfdng.
Stf chenh lech ap sua't tham thau do protein tao nen (ap sua't keo) giffa cac khu vtfc khac nhau trong cd the la mot ye'u to'quan trong quye't dinh stf van chuyen ntfdc giffa cac khu vtfc nay.
Protein trong huyet ttfdng tao ap sua't keo, anh htfdng ddn stf van chuyen ciia ntfdc va chat dien giai giffa khu vtfc noi bao va khu vtfc ngoai bao.
Ap suat tham thau dtfdc xac dinh bdi tdng so'phan tu* dtfdc hoa tan trong dich the.
Ddn vi do ciia ap sua't tham thau la miliosmole (mOsm)/kg ntfdc ciia huye't ttfdng.
1.5.1.2. Ap sua't thiiy tTnh
Ap sua't thiiy tinh la ap ltfc ciia dong mau ep vao thanh mach (huyet ap) hay ap ltfc ciia ntfdc ep vao mang tdbao. Neu xet ve phtfdng dien van chuyen ntfdc giffa cac khu vtfc, ap suat thiiy tinh cd xu htfdng day ntfdc ra khoi vung ma nd tac dung, cd htfdng tac dung ngtfdc lai vdi
ap sua't tham thau. Ap suat thiiy tinh trong cac tdbao day ntfdc qua mang te'bao ra ngoai.
2. CAC CHAT VO CCf TRONG Ctf THE
Cha't vo cd khi hoa tan trong dich cd the cd the phan ly thanh cac ion nen dtfdc goi la chat
dien giai. Ndng do chat tan trong cd the thay ddi tuy theo khu vtfc ; natri la cation chii ye'u ciia dich ngoai bao; kali la cation chii ye'u cua dich ndi bao. Tong so' cation trong cd the phai bang tdng so'anion (can bang dien tich).
Ltfc ke't hdp ciia cac chat dien giai dtfdc tinh bang ddn vi mEq.
2.1. Mot so' chat vo cd quan trong co trong cd the
Trong cd the sinh vat, cac cha't vd cd quan trong nhat la Na+, K+, Ca4"*, CI", Mg++, S042\
P043" va HC03"
2.1.1. Natri (Na+)
- Natri la cation chii yeu ciia dich ngoai bao (90%), ndng do trong huydt thanh binh
thtfdng la 135-146mEq/L.
Natri dong vai trd quan trong trong viec dieu hda ap sua't tham thau, thang bang acid- base. Natri con hoat hda enzym amylase va tfc chd hoat dong ciia phosphorylase. Trong cac mo, Na+ lien ke't vdi ntfdc, CI", HC03", PO43". Natri anh htfdng den stf din truyen xung dong than kinh
va sdi cd.
- Stf hap thu va bai tie't natri cd lien quan den stf hap thu va bai tie't ciia ntfdc, K+ va CI".
Hormon aldosterol gay tang stf tai hap thu natri.
- Nhu cau dtfdc dam bao chii ye'u nhd NaCl. Ngtfdi trtfdng thanh can mdi ngay 4 -5g natri, ttfc la 10 -12g NaCl, bang 10% ltfdng natri toan phan chtfa trong dich gianbao ciia cd the ngtfdi.
- Khoang 95% Na+ dtfdc bai xua't qua ntfdc tidu, mot phan nhd dtfdc dao thai qua md hoi
va phan.
- Tinh trang giam natri huye't co the gay dong kinh, nhtfc dau, tang nhip tim, ha huyet ap,
chuot rut, kich thich va cd the hdn me.
- Tinh trang tang natri huye't dtfdc bieu thi bang stf mat ntfdc d dich ngoai bao cd trieu chtfngla khat ntfdc, kho mieng, tang nhip tim, tang huyet ap,ma't phtfdng htfdng, ao giac, co giat, kich dong, co the tien de'n non me.
2.1.2. Kali (K+)
- La cation chii ye'u ciia dich noi bao, ndng do binh thtfdng trong huye't thanh la 3,5-5,5 mEq/L. Ndng do kali trong te' bao la khoang 140mEq/L. Nhu cau binh thtfdng khoang 4g/ngay.
- Kali duy tri ap sua't tham thau va can bang dien giai trong te bao,dieu hda thang bang acid base. Nd cd anh htfdng den stfdin truyen xung dong than kinh cd va stf co cd tim.
- Kali dtfdc bai xua't khoang 80% qua than (20 - 40 mEq/L ntfdc tidu). Ltfdng con lai dtfdc
bai tiet qua phan.
- Cd chd feedback dieu hoa stf bai tie't natri ngtfdc vdi kali. Aldosterol tang stf tai hap thu natri va tang stf bai xua'tkali.
- Kali huyet tang do than giam bai xua't kali (trong tdn thtfdng than ,thieu nang vo thtfdng than ), hay nhap vao nhieu kali; cd the gay hi Ian, giam nhip tim, ydu cd, chuot nit, tieu chay,
loan nhip tim...
- Kali huye't thtfdng giam do stf bai xua't qua nhieu hay nhap vao khong du kali (sau khi md, tieu chay, thiing da day, ruot, ctfdng vo thtfdng than, diing thud'c ldi tieu....), cd the gay loan
• nhip tim, chdng mat, chuot nit, liet, budn non, non mtfa ...
2.1.3. Calci (Ca2+)
- Calci la muo'i vd cd cd nhieu nhat trong cd the, tham gia ca'u true va chtfc nang ciia xtfdng va rang, phan ldn dtfdi dang cac muo'i vd cd khong tan (calci phosphat , calci carbonat).
Calci la cation chii ye'u ciia dich ngoai bao.
- Khoang 50% calci trong huydt thanh d dang ion hda va cd hoat tinh hda hoc, phan con lai ke't hdp vdi protein (dac biet la albumin), ndng do calci binh thtfdng trong huyet thanh la 95 -
lOOmg/L.
- Calci ciing vdi phospho lam tang stfc manh va do ben ciia xtfdng, calci giiip duy tri ca'u triic mang te'bao, chtfc nang va do tham thau cua mang. Calci anh htfdng den stf kich thich va stf co ciia cd tim va cd xtfdng, tham gia din truyen xung dong than kinh.
- Calci con tham gia qua trinh dong mau, hoat hda cholinesterase va nhieu qua trinh quan trong khac.
- Phan ldn calci (70-90%) dtfdc dao thai qua phan, mot ltfdng nhd dtfdc dao thai qua than.
- Thie'u calci gay coi xtfdng, loang xtfdng. Ha calci-huye't gay tinh trang co giat, ro'i loan
cd che dong mau, chuot rut, lii Ian.
2.1.4. CIo (CI *)
- Cd chii ye'u d dich ngoai bao. Ndng do binh thtfdng trong huye't thanh la 97-106 mEq/L.
- Cung vdi Na+, CI" dong vai trd tao ap sua't tham thau giff ntfdc cho cd the va dieu hoa thang bang acid - base. Ngoai ra, CI" con tham gia tao HC1 dich vi, hoat hda ezym amylase.
- Stf phan bd', hap thu va bai xua't CI" la cac qua trinh thu dong cd lien quan den stf van chuyen chii dong ciia ion Na+.
- Ro'i loan chuyen hda clo kem theo ro'i loan chuyen hda natri.
2.1.5. Phosphor (P)
- Cd d moi td chtfc te' bao, 80% d xtfdng va rang dtfdi dang kdt hdp vdi calci, 10% trong mau va cd , 10% d cac td chtfc khac. Phospho cd trong cd the d dang phosphat vo cO hay hdp
chat hffu cd.
- Phosphat cd the ke't hdp vdi lipid, protid, glucid, acid nucleic va ATP.
- Tham gia hau he't cac qua trinh chuydn hda va cd mat trong he tho'ng dem phosphat giiip duy tri thang bang acid base.
2.1.6. Magne (Mg2+)
- Tham gia ca'u tao xtfdng, co cd va hoat hda enzym. Mg2+ tang gay ha Ca 2+ trong mau.
Mg2+ giam trong benh coi xtfdng, xd'p xtfdng, co giat.
2.2. Cac dang muo'i vo cd trong cd the 2.2.1. Muo'i hoa tan trong cac dich
Khi hda tan, muo'i vd cd phan ly thanh cac ion va co tac dung tao ra ap sua't tham thau rat
ldn.
2.2.2. Muo'i khong tan
Dd la cac muo'i tham gia ca'u tao xtfdng. Vi du: calciphosphat.
2.2.3 Muo'i phtfc hdp vdi protein
Vidu:
- Feritin la mot protein chtfa sat.
- K+, Ca"1-1" phtfc hdp vdi albumin.
2.3. Vai tro ciia muo'i vo cd trong cd thd
Mac dtf hien dien trong cac td chtfc cd the vdi mot ltfdng nho nhtfng cac muo'i vd cd dong
nhieu vai trd quan trong.
2.3.1. Tham gia ca'u tao t§' bao
Muo'i trong toan cd the chiem khoang 4 -5% the trong. Muo'i vd cd cd trong thanh phan ciia tat ca cac te bao va td chtfc, nhtfng phan pho'i khong deu, nhieu nhat la d cac td chtfc xtfdng va rang dtfdi dang muo'i khong tan.
2.3.2. Tao ap sua't tha'm tha'u
Ap suat tham thau ciia cac dich trong cd the dtfdc tao bdi cac ion nhtf Na+, K+, Ca^, CI", Mg4"*", S042", H2P04" va HC03"... Ap sua't nay cd anh htfdng rat ldn den stf phan bd' va van
chuyen cac dich trong cd the.
2.3.3. Duy tri thang bang acid-base
Muo'i vo cd tao hai he tho'ng dem quan trong trong cd the la he dem bicarbonat (H2C03 /NaHC03 ) va he dem phosphat (NaH2P04 / Na2HP04 ; KH2P04 / K2HP04) giiip cd the duy tri dtfdc thang bang acid-base
2.3.4 Binh on protein d trang thai keo trong te'bao va mo
Muo'i vd cd cd tac dung dac biet do'i vdi trang thai ly hda ciia cac protein trong te bao va mo. Mtfc do hda tan, khuech tan, hydrat hda va hda tan ciia nhieu loai protein phu thuoc vao ndng do ciia mot so' ion, do do chtfc phan sinh ly ciia te bao cung phu thuoc rat ldn vao ndng do va ty le ciia cac ion nhat la muo'i d dang phtfc hdp vdi protein.
2.3.5. Cac vai tro khac
- Hoat hda hay tfc chd hoat dong enzym Vi du: - CI", Na+, K+ kich thich hoat dong ciia enzym
- Cu++, Pb+, Hg+....kim ham hoat dong ciia enzym
- Tham gia ca'u tao cac coenzym (cobalt, kem, ltfu huynh), hemoglobin va cytochrom chtfa sat, hormon (iod tao T3, T4, kem tao insulin..).
- Tham gia qua trinh dong mau va dan truyen than kinh (Ca^, K+, Na+...).
2.4. Stf ha'p thu va bai xua't muo'i vd cd 2.4.1. Stf ha'p thu
-Cac mudi vd cd dtfdc dtfa vao cd thd chii ydu qua dtfdng tieu hda, ha'p thu qua ruot vao
mau ya phan phoi de'n cac cd quan theo nhu cau sinh ly.
-Mudi vd cd de tan trong ntfdc dtfdc ha'p thu dl dang va hoan toan qua ruot, (NaCl, KC1).
Mudi vo cd khd tan trong ntfdc dtfdc ha'p thu it.
- Sau khi dtfdc ha'p thu cung vdi ntfdc, mot phan mudi dtfdc giff lai trong cd quan va mo,
mot phan d lai trong mau. Stf giff lai mudi trong cac cd quan cd chon loc.
Vi du: Ca 2+, Mg 2+, PO 43- dtfdc giff lai nhieu trong xtfdng
2.4.2. Stf bai xua't
Muo'i vo cddtfdc bai xua't chu ye'u qua ntfdc tieu, md hdi.
Cac mudi khong dtfdc ha'p thu dtfdc dao thai qua phan nhtf Ca3 (P04)2, MgS04, kim loai
nang...
2.5 Can bang dien giai
CQng giong nhtf ntfdc, trong cd the, Itfdng chat dien giai nhap vao phai bang ltfdng chat
dien giai bai xua't (can bang dien giai).
Can bang dien giai, dac biet ddi vdi Na+, K+,Ca 2+ cd anh htfdng ldn den stf din truyen
xung dong than kinh, stf co cd va tinh tham thau cua mang te bao.
Ndng do chat dien giai trong cd the dtfdc diiu hda chii yeu qua stf bai tiet ciia than (ntfdc tieu),
da (md hdi) va ruot (phan), pho'i hdp vdi tac dong ciia hormon.
- Na / K+: Dtfdc dieu hda do hormon aldosterol. Aldosterol tang stf tai ha'p thu Na+ va
tang stf bai xua't K+.
- Ca2+: dtfdc dieu hda bdi hormon parathyroid (PTH). Khi ndng do Ca2+ trong mau qua
thap, PTH se tang qua trinh huy xtfdng de giai phdng Ca2+, tang ha'p thu Ca2+ ttf ruot va giam bai
xua't Ca2+ ttf than.
- CI": stf van chuyen chii dong ciia Na+ gay ra stf van chuyen thu dong ciia CI".
2.6. Ro'i loan can bang dien giai
2.6.1. Natri huyet tha'p: Ndng do natri trong mau thap cd the do non mtfa, tieu chay, rdi loan chtfc nang than, giam tiet aldosterol, bai tiet md hoi qua mtfc, nhap qua nhieu ntfdc din de'n stf tf
ntfdc trong cd the.
2.6.2. Natri huyet cao: Ndng do natri trong mau cao do mat ntfdc nhieu, sd't, tieu dtfdng (giam tie't ADH) din de'n stf ro'i loan he than kinh trung tfdng.
2.6.3. Kali huye't tha'p: Ndng do kali trong mau thap do tang tiet aldosterol, Idi tieu, ro'i loan chtfc nang than, non mtfa, tieu chay. Hau qua la bi ye'u cd, liet, ho ha'p khd, loan nhip tim.
2.6.4. Kali huye't cao: Ndng do kali trong mau cao (>12 mEq/L) cd the do ro'i loan chtfc nang han, giam tie't aldosterol. Hau qua cd the bi liet cd xtfdng, diet do tim ngffng dap.
3. SI/ TRAO DOI NUtfC VA CAC CHAT BlM GIAI
Trong cd the, ntfdc va cac cha't vo cd luon ddi mdi nhd qua trinh trao ddi.
Stf van chuyen ntfdc va cac cha't dien giai co lien quan mat thiet vdi nhau va chiu chi
phoi bdi nhieu yeu to' nhtf thanh mach, huye't ap, can bang Donnan va ap sua't do keo,tinh trang
thang bang acid base, hoat dong ciia cac td chtfc ....
3.1. Stf trao ddi ntfdc va cac cha't dien giai giffa cac khu vtfc
3.1.1. Can bang Donnan va ap sua't do keo - Dinh mat Donnan
Do'i vdi cac cha't phan ly cd phan ttf ltfdng nhd, qua trinh khue'ch tan se theo quy luat vat
ly nghia la ttf ndi cd ndng do cao sang ndi cd ndng do tha'p hdn.
Do'i vdi cac cha't keo co phan t* ltfdng ldn (nhtf hdn hdp protein va dang muo'i cua no) thi
rhi co-Na" hay CI" di qua dtfdc mang ban tha'm.
TW nghiem: Mot binh dtfdc ngan dgitfa bang mot mang ban tham Kh, cho dung d^h muo'i NaCl vao mot ben, muo'i se phan ly va cac ion Na* va CT se khuech t nqua mang de dằt dXtran. thai can bang dong. Sau dd. ne'u thay the' dung dich 6" mot ben cua mang bang dung
S : l d i i ằ Na+, Cf sa qua mang dl dang cdn ion keo R" khdng qua dtfdc.
Na+(b) CI "(b)
Na+ (b)
CP(b)
(D
Na+(a) R-(a)
Na+ (b) CI" (b)
(2)
Na+(a+x) FT (a) Cr(x)
Na+ (b-x) CI "(b-x)
(3)