Effects of ONO-3122 (an enhancer of PGH2 production) and OKY-1581 (an inhibitor of TXA2 production) on the vasopressin-induced water flow in the toad bladder.

The effects of 1-iodo-3-aminomethyl-5,6,7,8-tetrahydro-2-naphthol (ONO-3122) which increases endogenous PGH2, and sodium (E)-2-methyl-3-[4-3-pyridylmethyl)phenyl]-2-methylpropenoate (OKY-1581) which inhibits thromboxane A2 synthesis, on vasopressin-induced osmotic water flow in the bladder of the toad, Bufo bufo japonicus, were examined. ONO-3122 significantly inhibited the vasopressin-induced water flow at a concentration of 1 X 10(-4) M. OKY-1581 inhibited the vasopressin-induced water flow at 1 X 10(-6) M, but enhanced it at 1 X 10(-4) M. These results suggest that ONO-3122 indirectly inhibits the vasopressin-induced osmotic water flow in the toad bladder; that is, ONO-3122 causes an increase in the conversion of arachidonic acid into PGH2. These results also suggest that OKY-1581 at a low concentration suppresses the vasopressin-induced water flow due to inhibition of cyclooxygenase activity. Both ONO-3122 and OKY-1581 provide a useful means for studying the action of prostaglandins.