Retinol secretion by the lacrimal gland.

In order to determine the source of the retinol which has been identified in the tear fluid, the lacrimal gland ducts of rabbits and rats were cannulated and the collected lacrimal gland fluid was analyzed by high performance liquid chromatography. Retinol was identified in the lacrimal gland fluid of rabbits and rats, and it is concluded that the lacrimal gland is the source of retinol in the tears. Dose-response studies show that intravenously administered pilocarpine and intra-arterial acetylcholine stimulate secretion of retinol by the lacrimal gland. Intravenous administration of vasoactive intestinal peptide (VIP) also stimulates retinol secretion in a dose-response manner. These observations are similar to the effects of cholinergic drugs and VIP on protein secretion by the lacrimal gland.