Changes in chloride secretion rate and vascular perfusion in the rectal gland of the European lesser-spotted dogfish in response to environmental and hormonal stimuli

Chloride secretion rates of rectal glands taken from the European lesser-spotted dogfish Scyliorhinus canicula adapting to 70% and 120% sea water (SW) were significantly greater and less than, respectively, those in the control 100% SW group. C-type natriuretic peptide (CNP) significantly increased chloride secretion rates above basal values in 100% SW although angiotenisn II (ANG II) had no effect. Perfusion of the secretory epithelia in rectal glands from 70% SW lesser-spotted dogfish was significantly higher than in rectal glands from 100% and 120% SW lesser-spotted dogfish. Perfusion of rectal glands with ANG II had no effect on perfusion of the secretory epithelia, although CNP perfusion induced significantly greater perfusion of the secretory epithelia than all other treatments. It remains to be determined if a reduction in environmental salinity induces an increase in plasma concentration of CNP and hence an increase in rectal gland activity