Free amino acid mediated volume regulation of isolatedNoetia ponderosa red blood cells: Control by Ca2+ and ATP

Abstract

The ionic and metabolic requirements of cellular volume regulation and the free amino acid (FAA) efflux from hypoosmotically stressedNoetia ponderosa (Mollusca: Arcidae) red blood cells was studied. Deletion of Ca2+ from 50% ASW prevented cell volume regulation and decreased the FAA efflux. Addition of Co2+, Mn2+, or La3+ to 50% ASW increased volume regulation and the FAA efflux, while verapamil, a Ca2+ antagonist, inhibited volume regulation and the FAA efflux. Volume regulation by the blood cells has a metabolic component also since DNP or incubation of the cells at 4°C both inhibited volume regulation and the FAA efflux. Thus, the FAA permeability ofN. ponderosa blood cell membranes can be manipulated by altering seawater [Ca2+] or by indirectly modifying intracellular levels of ATP.