Cyclic nucleotide levels during spontaneous uterine contractions.

Abstract

Tissue levels of adenosine 3′,5′-cyclic monophosphate (cyclic AMP) and guanosine 3′,5′-cyclic monophosphate (cyclic GMP) were determined in uterine muscles frozen at various points during spontaneous contraction–relaxation cycles. No significant changes in cyclic nucleotide levels were detected at any of the stages of contraction studied. Exposure of uterine segments to 1 μM isoproterenol resulted in an eightfold increase in cyclic AMP levels but no change in cyclic GMP, whereas exposure to 2 mM theophylline resulted in a doubling of cyclic GMP levels and a 42% increase in cyclic AMP content. Thus, the methods used were capable of detecting changes in cyclic nucleotide levels when they did occur. It was concluded that changes in cyclic nucleotide levels do not play a role in the initiation or regulation of spontaneous contractions of isolated rat uterus.