Regulation of K+ transport in the rat distal colon via angiotensin II subtype receptors and K+ -pathways.
The role of angiotensin subtype-1 (AT1) and -2 (AT2) receptors in mediating the effects of angiotensin II (ANG II) on several K+ transporters was studied in rat distal colon using an Ussing chamber. Angiotensin II induced K+ secretion at two different doses. Secretion occurred at 10-(8) and 10-(4) M, as a result of an increase in serosal-to-mucosal flux (Js-m). The ANG II-induced stimulation of Js-m at a low dose (10-(8) M) was abolished by PD123319 while losartan did not alter the low-dose ANG II-dependent increase in Js-m. In contrast, the increase in Js-m induced by a high-dose of ANG II (10-(4) M) was blocked by losartan, whereas PD123319 partially reduced the stimulatory effect. In the presence of both blockers, high-dose ANG II induced an inhibition of basal Js-m. Low-dose ANG II activated the barium-sensitive K+ channels, whereas the Na+, K+, 2Cl- cotransporter and the Na+, K+ -ATPase pump were unchanged. At the high dose, ANG II activated the barium-sensitive K+ channels and the Na+, K+, 2Cl- cotransporter and inhibited the Na+, K+ -ATPase pump. These data indicate that ANG II stimulates serosal-to-mucosal K+ flux in the rat distal colon at high and low doses via different receptors and K+ transporters.
Grahnquist
L
L
Department of Paediatrics, Huddinge University Hospital and Department of Woman and Child Health, Astrid Lindgren Children's Hospital, Karolinska Institutet, Stockholm, Sweden.
Chen
M
M
Gerasev
A
A
Aizman
R
R
Celsi
G
G
D000804:Angiotensin II / Q000494:pharmacology*; D057911:Angiotensin Receptor Antagonists; D000818:Animals; D001693:Biological Transport, Active; D002352:Carrier Proteins / Q000378:metabolism; D003106:Colon / Q000187:drug effects* / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D007093:Imidazoles / Q000494:pharmacology; D066298:In Vitro Techniques; D019808:Losartan / Q000494:pharmacology; D008297:Male; D011188:Potassium / Q000378:metabolism*; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D044140:Receptor, Angiotensin, Type 1; D044139:Receptor, Angiotensin, Type 2; D011945:Receptors, Angiotensin / Q000378:metabolism*; D028021:Sodium-Potassium-Chloride Symporters; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism
D057911:Angiotensin Receptor Antagonists; D002352:Carrier Proteins; D007093:Imidazoles; D015221:Potassium Channels; D011725:Pyridines; D044140:Receptor, Angiotensin, Type 1; D044139:Receptor, Angiotensin, Type 2; D011945:Receptors, Angiotensin; D028021:Sodium-Potassium-Chloride Symporters; D000804:Angiotensin II; C073402:PD 123319; D000254:Sodium-Potassium-Exchanging ATPase; D019808:Losartan; D011188:Potassium