AJP - Regulatory, Integrative and Comparative Physiology, Vol 253, Issue 6 801-R808, Copyright © 1987 by American Physiological Society
Vasoactive intestinal peptide stimulates ion transport in avian salt gland
R. J. Lowy, J. H. Schreiber and S. A. Ernst
Department of Anatomy and Cell Biology, University of Michigan Medical School, Ann Arbor 48109.
Avian salt glands are considered to be under the control of cholinergic
nerve fibers. Here we report evidence that vasoactive intestinal peptide
(VIP) also regulates ion transport. Nerve fibers stained
immunocytochemically with anti-VIP were distributed throughout the tissue
within the peritubular connective tissue and were in close proximity to the
secretory tubules. VIP applied to primary cultures of the secretory cells
elicited active ion transport as assayed by short-circuit current (Isc)
analysis. The mucosal-to-serosal positive Isc was produced in a
dose-dependent fashion [(EC50) = 3.1 X 10(-9) M], was potentiated by
theophylline, and was inhibited by either ouabain or furosemide. This Isc
was independent of activation by cholinergic agonists. VIP also increased
ouabain-sensitive respiration 14-18% in acutely isolated cells from
salt-stressed and unstressed animals. These data demonstrate for the first
time that VIP is present in the avian salt gland and can act as a
secretagogue by directly affecting the secretory cells. In addition, the
results provide evidence for direct control of ion transport by an
adenosine 3',5'-cyclic monophosphate-linked neurohormone in both adult
unstressed and fully salt-stressed animals.
