Erythrocytes may synthesize their own nitric oxide.

The ability of hemoglobin and myoglobin to bind nitric oxide (NO) produced by other cells and circulating vasodilators is well known. To characterize erythrocytes (RBCs), we used NADPH diaphorase labeling, as well as antibodies to the three known types of NO synthase (NOS 1, 2, and 3), and to a molecule usually associated with NOS, calmodulin. We show that the NADPH-diaphorase label labels myenteric neurons, endothelial cells, and the blood cells trapped in the lumen of the blood vessels running through the intestinal wall. The myenteric neurons are also positive for neuronal NOS (NOS1), calmodulin, and neuropeptide Y, indicating that they are NO-producing neurons. Endothelial cells are positive for NOS3 (a constitutive form of NOS), while macrophages and lymphocytes are positive for NOS2 (an inducible form of NOS). All are positive for calmodulin. Surprisingly, the RBCs are positive for NOS2 and 3, as well as calmodulin. Thus the RBCs possess all the cellular machinery to synthesize their own NO. We suggest that erythrocytes would synthesize and use NO to modulate their own physiology.

Neurons from neonatal hypertensive rats exhibit abnormal membrane properties in vitro.

The in vitro membrane properties of neurons from superior cervical ganglia (SCG) of neonatal spontaneously hypertensive (SH), Wistar-Kyoto (WKY), and Sprague-Dawley (SD) rats were studied with microelectrodes. Neurons were obtained by enzymatic dissociation, plated, irradiated, and studied after 2-5 wk. Most SH neurons showed multiple action potentials in response to an intracellular long-duration depolarizing pulse (multiple firing), whereas most neurons from WKY or SD rats generated only one or two action potentials. Multiple firing was inhibited by low concentrations of cobalt (10(-5) M) but not by tetrodotoxin (TTX) (3 x 10(-6) M). Neither high calcium (5-10 x 10(-3) M) nor the Ca2+(-)channel opener BAY K 8644 (10(-6) M) could induce multiple firing in SD or WKY neurons. However, multiple firing was readily induced by apamin (10(-6) M) or tetraethylammonium chloride (5 x 10(-3) M) (Ca2+(-)activated K+(-)channels blockers), with cobalt and TTX sensitivities similar to native multiple-firing neurons. We conclude that 1) multiple firing is characteristic of neonate SH rats SCG neurons in vitro and depends on regenerative Ca2+ currents; 2) multiple firing in SH neurons results from a lack of activation of a Ca2+(-)activated K+ conductance and not from a lack of internal Ca2+ availability; and 3) multiple firing in SCG neurons mirrors a default in K+ conductance common to all cells in genetically hypertensive individuals.