AJP - Regulatory, Integrative and Comparative Physiology, Vol 246, Issue 1 67-R71, Copyright © 1984 by American Physiological Society
In vivo effect of volume expansion on rectal gland function. II. Hemodynamic changes
R. J. Solomon, M. Taylor, R. Rosa, P. Silva and F. H. Epstein
Intravascular volume expansion causes a 300% increase in the rate of fluid
secretion from, and blood flow to, the in vivo rectal gland of the spiny
dogfish Squalus acanthias. Similar increases are also observed in explanted
rectal glands perfused through a catheter from the dorsal aorta of a
volume-expanded dogfish. Stimulation of rectal gland secretion by volume
expansion is not associated with a change in the ratio of chloride secreted
to oxygen consumed by the rectal gland and the oxygen extraction ratio,
suggesting that an increase in blood flow is necessary to support the
increased rate of chloride secretion. Perfusion of the explanted gland with
bumetanide (10(-4) M) completely inhibits the secretory response to volume
expansion but does not prevent the increase in blood flow. Bumetanide also
inhibits dibutyryl adenosine 3',5'-cyclic monophosphate- and
theophylline-induced increases in chloride secretion but does not inhibit
the hyperemic response. Somatostatin inhibits the secretory response of the
explanted gland to volume expansion but does not prevent the increase in
blood flow. Although an increase in blood flow is necessary to support the
increased energy requirement of enhanced transport, the secretory response
and the increase in blood flow appear to be independently regulated and
mediated, at least in part, by humoral factors.
