Cholinergic, adrenergic, and PGE1 effects on cyclic nucleotides and growth in cultured corneal epithelium.

Effects of adrenergic and cholinergic drugs and prostaglandin E1 on cyclic nucleotide accumulation and parameters of growth and basement membrane synthesis were examined in corneal epithelial cell cultures. 8-bromo-cGMP significantly (p less than 0.05) enhanced incorporation of labeled thymidine and leucine, as did acetylcholine and carbamylcholine, which elevated cGMP and decreased cAMP/cGMP ratio. Responses to acetylcholine were abolished by atropine and alpha-bungarotoxin. Precursor incorporation was inhibited by dibutyryl cAMP and adenosine 5'-monophosphate and by norepinephrine, epinephrine, prostaglandin E1, and theophylline, which significantly elevated cAMP levels and cAMP/cGMP ratio. Propranolol, but not phenoxybenzamine, blocked responses to effective concentrations of norepinephrine. Norepinephrine, PGE1, and dibutyryl cAMP also significantly elevated uptake of labeled glucosamine and incorporation of labeled proline into collagenase-sensitive protein or the hydroxyproline fraction of protein hydrolysates, while acetylcholine had no effect on parameters of basement membrane synthesis. Propranolol blocked responses to norepinephrine. Results were consistent with a cGMP-mediated stimulatory role of the cholinergic transmitter in corneal epithelial growth regulation, cAMP-mediated beta-adrenergic suppression of regrowth and increased basement membrane production after initial injury to the corneal epithelium, and potentiation of the adrenergic effect by prostaglandins.