Nitric Oxide Synthase in Human Parathyroid Glands and Parathyroid Adenomas

Nitric oxide (NO) is a novel gaseous intercellular transmitter thought to play important physiological roles in the regulation of blood flow and hormone secretion in, for example, the pituitary, the thyroid, and the endocrine pancreas. Whether nitric oxide synthase (NOS) is present in the human parathyroid glands has not yet been demonstrated. In the present study, histologically normal, but functionally suppressed human parathyroid glands and parathyroid adenomas from patients with primary hyperparathyroidism were investigated by immunocytochemistry with antibodies against neuronal NOS and by reduced nicotinamide adenine dinucleotide phosphate (NADPH) diaphorase histochemistry. We also used H&E to identify the NOS-immunoreactive cells. Immunocytochemistry demonstrated the presence of neuronal-type NOS in a subpopulation of glandular cells, identified as oxyphilic cells, in both normal parathyroid glands and adenomas. NADPH-diaphorase staining visualized NOS in the endothelium of blood vessels and in glandular cells, corresponding to those containing immunoreactive NOS. In addition, we found NADPIH-diaphorase staining in many chief cells. Our results indicate that both glandular cells and vascular endothelium in human parathyroid glands and adenomas express NOS. There is thus a morphological substrate for locally produced NO that may be involved in the regulation of parathyroid blood flow and hormone secretion.