Acid secretion, potential difference, and resistance of elasmobranch stomach

¹ Marineland Research Laboratory, Marineland, Florida, and Department of Physiology, University of Louisville School of Medicine, Louisville, Kentucky

The present report is concerned with in vitro studies on gastric mucosa of the skate, Raja eglentaria, the electric ray, Narcine braziliensis, and the shark, Negaprion brevirostris. Maximum secretory rates of from 0.65 to 2.7 µEq hr^–1 cm^–2 were found. An increase in the secretory rate from an initial low level was associated with an increase in potential difference (PD), a decrease in resistance, and an increase in the calculated short-circuit current. The average PD and resistance before the increase in the secretory rate was 2.2 mv (nutrient positive) and 268 ohms cm². After the increase they were 6.4 mv and 199 ohms cm². Thiocyanate (10^–2 m) to nutrient resulted in a decrease of secretory rate to zero and an increase in PD and resistance. The results can be explained on the basis of the separate mechanisms theory of H⁺ and Cl^– ion secretion on the assumption that the resistance in the Cl^– ion limb of the circuit is considerably lower than that in the H⁺ ion limb of the circuit.

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