Secretory effect of prostaglandins on the rabbit lacrimal gland in vivo.

Fluid secretion from the cannulated excretory duct of the rabbit lacrimal gland was collected in microcapillary pipette at 10 min intervals. Secretion rate and electrolyte concentrations (Na+, K+ and Cl-) in the lacrimal fluid samples were determined before and after injections of small doses of prostaglandins (PGE1, PGE2, PGF1 alpha, PGF2 alpha, 15 epi-PGF2 alpha, PGF2 beta, PGA1 & PGA2) into the external maxillary artery. Only PGE1 had a dose-dependent stimulatory effect on the lacrimal gland secretion. The maximum secretion rate which was induced by PGE1 (25 micrograms/kg) was 7.2 +/- 0.9 microliters/10 min. Na+ concentration in the fluid secretion stimulated by PGE1 was increased; however, K+ and Cl- concentrations were not changed. Pretreatment with atropine (50 micrograms/kg, I.A.) failed to prevent the stimulatory effect of low doses of PGE1. On the other hand, the secretory responses were abolished when propanolol (3 mg/kg, I.A.) was administered prior to PGE1. The results suggest that fluid secretion of the rabbit lacrimal gland in response to PGE1 may be caused by excitation of the sympathetic ganglia and/or by direct action on beta-receptors in the acinar cells.