In vivo modulation of rat distal tubule net HCO3 flux by VIP, isoproterenol, angiotensin II, and ADH
Levine, D.Z.; Iacovitti, M.; Buckman, S.; Harrison, V.
American Journal of Physiology 266(6 Pt 2): F878-F883
1994
ISSN/ISBN: 0002-9513 PMID: 8023967 Document Number: 424387
To examine the in vivo effects of agonists reported to influence bicarbonate flux (J-tCO-2), microperfusion experiments were carried out on distal tubules of normally fed or overnight-fasted rats. As we previously reported, distal tubules from fed rats reabsorbed no bicarbonate, whereas overnight-fasted rats consistently reabsorbed bicarbonate (J-tCO-2 10 +- 3 pmol cntdot min-1 cntdot mm-1; P lt 0.01). Vasoactive intestinal peptide and isoproterenol infused intravenously (7.3 and 4.0 mu-g cntdot kg1-1 cntdot h-1, respectively) in fasted rats suppressed J-tCO-2 and, in the case of vasoactive intestinal peptide, elicited net bicarbonate secretion (J-tCO-2 - 10 +- 2 and -4 +- 4 pmol cntdot min-1 cntdot mm-1, respectively). In fed - rats, angiotensin II infused at a rate of 1.2 mu-g cntdot kg-1 cntdot h-1 stimulated bicarbonate reabsorption (J-tCO-2, 16 +- 3 pmol cntdot min-1 cntdot mm-1), while antidiuretic hormone infused at 0.024 mu-g cntdot kg-1 cntdot h-1 elicited a similar response (17 +- 4 pmol cntdot min-1 cntdot mm-1), both values being significantly different from control. These results, therefore, demonstrate for the first time that these agonists can modulate J-tCO-2 at the distal tubule site in vivo and therefore may be potential regulators of systemic acid-base balance.