Effect of [formula omitted] phosphate on the short-circuiting current in the turtle bladder

Abstract

1. 1. Addition of p- nitrophenyl phosphate (final concentration, 4.0 mM) to a glucose-enriched serosal fluid of the short-circuited bladder of Pseudemys scripta is followed by a decrease in the short-circuiting current ( I sc ) to half the control level after about 45 min; and concomitantly, in the generation of p- nitrophenol which reaches concentrations of 0.03–0.06 mM in the serosal fluid after 45–60 min. The pattern of decline of I sc follows that of accumulation of p- nitrophenol in the serosal fluid 2. 2. Identical additions of p- nitrophenyl phosphate to glucose-free serosal fluids have no effect on I sc over and above the usual decline occasioned by removal of glucose per se. 3. 3. Addition of p- nitrophenyl phosphate to the mucosal bathing fluid is not followed by decreases in I sc , and fails to induce the appearance of p- nitrophenol . 4. 4. Direct addition of the phenols, p- nitrophenol or 2,4-dinitrophenol, to the serosal or to the mucosal bathing solution is also followed by a decrease in I sc to half its control level after 50–60 min; an effect elicited when the final concentration of p- nitrophenol is 1.0 mM, but not when the final concentration is 0.1 mM. 5. 5. The mean times required for 50% inhibition of I sc by p- nitrophenyl phosphate, p- nitrophenol and 2,4-dinitrophenol: 42, 58, and 44 min respectively are not significantly different from one another ( P > 0.1) 6. 6. It is suggested that serosal p- nitrophenyl phosphate is hydrolyzed by a membrane-bound phosphatase to its phenolic product p- nitrophenol which interferes with mitochondrial ATP production and consequently with the energy supply for maintenance of Na + transport.