Role of nitric oxide in neurally induced pancreatic exocrine secretion in pigs

Formation of NO, enzymatically catalyzed by NO synthases in both endothelial cells and autonomic nerves, seems to explain some noncholinergic nonadrenergic tissue reactions. We studied the possible role of NO in vagally induced pancreatic exocrine secretion using isolated perfused porcine pancreas (n = 11) with intact vagus nerve (VN) supply. Electrical stimulation of the VN (8 Hz, 10 mA) and infusions of vasoactive intestinal polypeptide (VIP, 2 x 10(-9) M) were carried out before and after addition to the perfusate of the NO synthase inhibitors N omega-nitro-L-arginine methyl ester (L-NAME, 10(-4) M) or NG-nitro-L-arginine (L-NNA, 10(-5) M) with and without further addition of L-arginine (10(-3) M). We also studied the effects of L-arginine alone and of sodium nitroprusside (10(-4) M). In all experiments VN and VIP caused a profuse exocrine secretion (43 +/- 7 and 44 +/- 11 times basal secretion). The inhibitors increased vascular resistance approximately twofold but had no effect on the vascular relaxation caused by VIP and VN. The exocrine fluid response to VN was reduced to 19 +/- 5 and 4.7 +/- 1.8% (L-NAME and L-NNA), and response to VIP was reduced to 54 +/- 12 and 35 +/- 13%. Protein and bicarbonate outputs largely paralleled flow rate. Addition of L-arginine (no effects alone) to L-NAME restored the responses to VN (to 100 +/- 21% of controls) and increased VIP responses (to 65 +/- 11%).(ABSTRACT TRUNCATED AT 250 WORDS)