AJP - Regulatory, Integrative and Comparative Physiology, Vol 248, Issue 5 638-R640, Copyright © 1985 by American Physiological Society
Primary role of volume expansion in stimulation of rectal gland function
R. Solomon, M. Taylor, S. Sheth, P. Silva and F. H. Epstein
Chloride secretion by the in vivo rectal gland of the shark is stimulated
by the intravascular infusion of salt solutions of varying osmolar and
sodium concentration. In a cross-perfused and denervated rectal gland, the
infusion of a small amount of a hypertonic salt solution raises plasma
osmolality but does not increase plasma volume in the donor fish. Under
these conditions, rectal gland chloride secretion is not stimulated. A
subsequent infusion of isotonic shark Ringer solution increases plasma
volume 50%, decreases plasma osmolality, and produces a fourfold increase
in chloride secretion and a threefold decrease in vascular resistance
within the gland. Both the vasodilatory and secretory responses also follow
the infusion of a hypotonic shark Ringer solution. The data further support
the hypothesis that the rectal gland of the shark is involved in the
regulation of intravascular volume rather than in osmoregulation.
