Site of origin of an urinary Na-K-Cl cotransport inhibitor.
We investigated the site of origin of a potent inhibitor of the Na-K-Cl cotransport system (CIF), which has been previously identified in urines from salt-loaded rats. Rats were given a 2% NaCl solution to drink for 15 and 60 days and the plasma was obtained and tested for cotransport inhibitory activity (on bumetanide-sensitive Li+ efflux in Li-loaded human erythrocytes) in dose-response curves. The IC50 for cotransport inhibition (vol:vol dilution reducing cotransport activity by 50%) was found to be 26.5 +/- 7.2 (mean +/- SEM, n = 5) and 6.9 +/- 0.7% (n = 10) on days 15 and 60, respectively (control samples, day 0, only inhibited about 20% cotransport activity at a 30% plasma vol:vol dilution, n = 7). Organ extracts from salt-loaded rats were prepared and tested for cotransport inhibitory activity. A statistically significant cotransport inhibitory activity was only found in pituitary extracts (-36 +/- 3 vs. -5 +/- 4% in control rats, n = 4, p < 0.01). Dissection of a large number of pituitary glands from salt-loaded rats revealed CIF activity only in the neurohypophysis (cotransport inhibition -46.5 +/- 5.2 vs. -0.5 +/- 16.4% in the anterior lobe, n = 4, p < 0.05). In conclusion, CIF is a new circulating endogenous factor, probably secreted by the neurohypophysis.
Alda
J O
JO
Departamento de Fisiologia, Facultad de Medicina, Zaragoza, España.
Alvarez-Guerra
M
M
Lou
M
M
Gimenez
I
I
Soler
A
A
Garay
R P
RP
D000315:Adrenalectomy; D000818:Animals; D002352:Carrier Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism / Q000652:urine; D002712:Chlorides / Q000378:metabolism; D006498:Hepatectomy; D006801:Humans; D007016:Hypophysectomy; D008297:Male; D045283:Natriuretic Agents / Q000502:physiology* / Q000652:urine*; D010902:Pituitary Gland / Q000378:metabolism; D011188:Potassium / Q000737:chemistry; D051381:Rats; D012964:Sodium / Q000378:metabolism; D012965:Sodium Chloride / Q000494:pharmacology; D028021:Sodium-Potassium-Chloride Symporters; D014020:Tissue Extracts / Q000378:metabolism
D002352:Carrier Proteins; D002712:Chlorides; D045283:Natriuretic Agents; D028021:Sodium-Potassium-Chloride Symporters; D014020:Tissue Extracts; D012965:Sodium Chloride; D012964:Sodium; D011188:Potassium