Ethanol-Induced Release of Adenosine 3′,5′-Monophosphate into the Medium by Rat Testis in Vitro*

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Abstract
The effects of LH, ethanol, and acetaldehyde on the in vitro release of cAMP into the medium from decapsulated rat testes were studied, and the data were correlated with other measured parameters, such as the total tissue cAMP and the binding of 125I-labeled hCG to testicular receptors. The concentration of cAMP in the medium after incubation of the testes with low concentrations of LH (50 ng/testis) for 2 h at 27 C was found to be 81.6 ± 3.8 pmol/testis compared to 43.6 ± 2.9 pmol in controls (an 87% stimulation). The release of cAMP from the testis was not accompanied by a detectable decrease in 125Ilabeled hCG binding as predicted by the occupancy theory of hormone receptor interactions. Tissue levels of cAMP were maintained at 100 ± 2.5 pmol/testis. High concentrations of hormone did not further increase the release of cAMP, but the receptor sites were decreased. Treatment of decapsulated rat testes with ethanol (10%, vol/vol) under similar experimental conditions resulted in a 71% increase in cAMP levels in the medium. The tissue cAMP levels were also elevated in test groups. Binding patterns were comparable to those in controls. FSH and acetaldehyde had no effect on any of the above parameters. High concentrations of ethanol (>10%) decreased the number of receptors, with a loss of biological response. Kinetic experiments revealed that maximal stimulation of cAMP production (115 ± 12 pmol/testis) by 10% ethanol occurred 30 min after incubation. The tissue cAMP levels and the binding sites for hCG did not substantially differ from those values reported in previous experiments with ethanol. On the basis of the present observations, it is suggested that hormone and ethanol activate the tissue by altering the characteristics of the membrane; receptor occupancy may not be required for biological response.