Electrogenic Na+ transport in rat late distal colon by natural and synthetic glucocorticosteroids (original) (raw)

The American journal of physiology, 1999

Abstract

The potency of in vitro-added corticosteroids to stimulate electrogenic Na+ absorption (JNa, the Na+ absorptive short-circuit current blockable by 10(-4) M amiloride) was determined in rat late distal colon. JNa was determined 8 h after steroid addition from the drop in short-circuit current caused by 10(-4) M amiloride. The concentration dependency of JNa was obtained for seven corticosteroids and compared with that established for aldosterone. Apparent mineralocorticoid potencies as determined from apparent Michaelis-Menten constant (Km) values were as follows: aldosterone 1. 2 nM > RU-28362 20 nM = deoxycorticosterone 20 nM > deoxycortisol 36 nM >/= dexamethasone 37 nM > corticosterone 170 nM > cortisol 210 nM. These steroids exhibited Vmax values of 9-13 micromol. h-1. cm-2 and similar concentration dependencies. Hill coefficients were between 1.6 and 2.1, suggesting cooperative effects between activated receptors. We conclude that corticosteroids exhibit graded m...

Ingo Grotjohann hasn't uploaded this paper.

Let Ingo know you want this paper to be uploaded.

Ask for this paper to be uploaded.