Response by the corpuscles of Stannius to hypotensive stimuli in three divergent ray-finned fishes (Amia calva, Anguilla rostrata, and Catastomus commersoni): cardiovascular and morphological changes

Abstract In accordance with their vital role in cardiovascular physiology ( Butler and Zhang, 2001 ) corpuscles of Stannius (CS) from two teleosts and an holostean species showed marked and consistent degranulation and exocytotic responses to hypotensive stimuli. In eels ( Anguilla rostrata LeSueur) acute blood withdrawal (hypovolemic hypotension) was followed by a prompt decrease in cardiac output (CO) and dorsal aortic pressure ( P DA ), a compensatory tachycardic response and an increase in systemic vascular resistance ( R SYS ). Isovolemic hypotension induced by papaverine i.v, led to a similar, but more prolonged, decrease in P DA but the heart rate (HR) continued to accelerate, thereby counterbalancing the severe and persistent decrease in R SYS . Both hypovolemic and isovolemic hypotension were followed by a significant depletion of cytoplasmic granules from eel CS even though plasma concentrations of Ca, Mg, Na + , and K + were normal. In an ancient holostean fish, the bowfin, Amia calva and a generalized teleost fish, Catastomus commersoni , the number of cytoplasmic granules decreased by 39% and 54%, respectively, 120 min after the acute withdrawal of 8 ml kg bw −1 of blood. These findings suggest that a primary role of the CS is to release cytoplasmic granules containing renin or isorenin into the blood circulation, in response to hypotension and/or hypovolemia.