Involvement of cyclic nucleotides in the beating response of rat heart cells in culture

Abstract

The relationships of cyclic adenosine 3′,5′-monophosphate (cyclic AMP) concentration and cyclic guanosine 3′,5′-monophosphate (cyclic GMP) concentration to beating behaviour of cultured rat heart cells are reported. Cyclic AMP has a positive chronotropic effect and cyclic GMP has a negative inotropic effect on the beating of cultured rat heart cells. Rate and intensity of beating were measured using an automatic light sensitive monitor. Cultured cells were treated with cardioactive drugs until a physiological response was observed and recorded on the monitor at which time the cells were analyzed for cyclic AMP and cyclic GMP concentrations. Direct addition of dibutyryl cyclic AMP and cyclic GMP resulted in an increase in the rate of beating and a decrease in beating intensity, respectively. Both cyclic nucleotides affected rate and intensity of beating but significant relationships could be obtained only between cyclic AMP vs rate and cyclic GMP vs intensity.