Retinoids increase the response of guinea pig but not human keratinocytes to agonists of adenylate cyclase in vitro.

Primary cultures of adult human and guinea-pig keratinocytes were treated with various retinoids for up to 7 days. The cells were exposed to 3H-adenine and then challenged with several agonists of adenylate cyclase. 3H-labeled adenine nucleotides were extracted and 3H-cAMP purified chromatographically. All retinoids increased the formation of 3H-ATP from 3H-adenine and the conversion of 3H-ATP to 3H-cAMP by guinea-pig cells, the extent being dependent on the particular retinoid and agonist used. Human cells were relatively sensitive to isoproterenol and not to prostaglandins or histamine, but their response was little affected by retinoids. Guinea-pig cells were most sensitive to prostaglandins. The proliferogenic effects of retinoids on the latter cells may be mediated by increased sensitivity to agonists leading to generation of cAMP.