Does nitric oxide act as a cellular messenger in muscarinic endometrial secretion in the guinea-pig?

Uterine secretory cells receive a sympathetic cholinergic secremotor innervation. Nitric oxide (NO) has been suggested to be a second messenger of neurogenic modulated glandular secretion of the seminal vesicle. Thus a similar pattern for nervous induced carbohydrate secretion of the endometrium was assumed. The nitric oxide synthase (NOS) activity was estimated via formation of L-citrulline from L-arginine and histochemically with the nicotinamide-adenine dinucleotide phosphate diaphorase (NADPH-d) nitro blue technique. The carbohydrate secretion from everted uterine horns placed in organ baths was estimated. A calcium dependent formation of citrulline was found in the uterine horn suggesting an NOS activity. Strong NADPH staining cells were found in the glandular ducts of the endometrium and in the epithelial linings of the oviduct. Carbachol induced carbohydrate secretion of the endometrium while N-nitro L-arginin (L-NNA) and N-nitro L-arginin methyl ester (L-NAME) inhibited the carbachol induced secretion. The isomer D-NAME had no effect on carbachol induced secretion. When L-arginine was administered together with L-NNA no inhibitory effect on carbachol induced secretion was seen. L-arginine only had no effect on carbohydrate secretion. The NO donor glyceryl tritrate increased carbohydrate secretion but no synergistic effect was seen in combination with carbachol. The results suggest that glandular NO production is a prerequisite for muscarinic carbohydrate secretion of the endometrium.