Activation of adenylate cyclase during swelling of S49 cells in hypotonic medium is not involved in subsequent volume regulation.

Experiments in S49 mouse lymphoma cells indicate that adenylate cyclase activity is increased following swelling in hypotonic medium through a mechanism independent of the G-proteins which are involved in hormonal regulation of the enzyme. An intact actin cytoskeleton is apparently required for stimulation of adenylate cyclase by mechanical forces. It was hypothesized that this increase in cAMP may be involved in triggering subsequent volume regulatory events. Manipulation of intracellular cAMP content and protein kinase A activity in S49 cells prior to swelling or during the regulatory volume decrease following swelling provided no evidence of a significant role for cAMP in regulating the extent of initial volume increase or the subsequent regulatory volume decrease. Treatment of S49 cells with 10-200 microM miconazole, previously shown to inhibit adenylate cyclase activity, attenuated the initial volume increase with medium dilution and accelerated the rate of regulatory decrease in a dose-dependent and time-dependent manner. However, incubation with 100 microM miconazole for 20 min, which completely inhibited swelling-induced increases in cAMP content, had no significant effect on either the initial volume expansion or the extent of regulatory volume decrease.