EVANS, A.N.*; HENNING, T.M.; NUNEZ, B.S.; University of Texas Marine Science Institute, Port Aransas, TX; University of Texas Marine Science Institute, Port Aransas, TX; University of Texas Marine Science Institute, Port Aransas, TX: Sequence and tissue distribution of AII receptor mRNA in the euryhaline stingray, Dasyatis sabina
It is well established that angiotensin II (AII), a key element of the renin-angiotensin system (RAS), plays a major role in the maintenance of salt and water balance in mammals. AII elicits its effects in part by stimulating mineralocorticoid (MC) synthesis in adrenocortical cells; MCs subsequently act as antinatriuretic factors. The presence of a RAS similar to that in mammals has only recently been demonstrated in elasmobranchs, though conflicting evidence has been presented regarding its role in regulating the synthesis of the elasmobranch mineralocorticoid (1-alpha hydroxycorticosterone; 1-alpha B). To better define the role of AII in elasmobranch osmoregulation, we used degenerate primers in coupled reverse transcription/polymerase chain reactions (RT-PCR) to isolate AII receptor (AT1) mRNA sequence from the interrenal gland of the euryhaline elasmobranch Dasyatis sabina. The rapid amplification of cDNA ends (RACE) PCR technique was used to obtain additional AT1 sequence. Preliminary analysis of cDNA clones suggests that there are at least two forms of the elasmobranch AT1 receptor in D. sabina. Total RNA was isolated from a suite of tissues obtained from freshwater (FW) and saltwater (SW) adapted D. sabina to evaluate tissue-specific AT1 expression. RT-PCR indicates that AT1 is expressed in the central nervous system, digestive tract, circulatory system and osmoregulatory tissues of both FW and SW adapted D. sabina. The expression of AT1 in such a wide range of tissues strongly suggests that AII plays a significant role in elasmobranch physiology.
