Enzyme histochemical expression of nicotinamide adenine dinucleotide phosphate-diaphorase in paranal sinus, external and internal anal sphincters in dogs

The present study showed the sites of histochemical expression of nicotinamide adenine dinucleotide phosphate-diaphorase - NADPH-d in the different parts of canine paranal sinus. Keratinocytes in the basal and spinous layers exhibited a moderate to strong reaction whereas those in the upper layers – a weak enzyme histochemical reaction. No enzyme reaction was observed in stratum corneum. NADPH-d expression in secretory and myoepithelial cells of apocrine glands was moderate to strong. Sebaceous glands reaction was moderate to strong in peripheral sebocytes and weak to absent in central ones. The endothelium of blood vessels located in the subepithelial and subglandular connective tissue of the paranal sinus wall showed a moderate degree of enzyme histochemical activity. The longitudinal cross section of the external anal sphincter revealed areas of muscle fibres sarcolemma and perinuclear cytoplasmic zones with moderate to strong enzyme reaction. Strong enzyme activity of nitrergic nerve fibres was detected in the internal anal sphincter. This investigation was the first to show a marked NADPH-d activity in the various structures of canine paranal sinus that was probably involved in nitric oxide synthesis related to physiological and pathological events in this organ.