Nitric oxide synthase isoform activities in kidney of Dahl salt-sensitive rats.
An abnormal L-arginine-nitric oxide axis has been suggested to be relevant to the genesis of salt-sensitive hypertension. In the present study we investigated the activities of three isoforms of nitric oxide synthase (NOS) in the kidney of Dahl salt-sensitive and salt-resistant rats. Five-week-old Dahl Iwai salt-sensitive (n = 9) and salt-resistant (n = 10) rats were maintained on a high salt diet (4% sodium chloride) for 4 weeks. We measured calcium-dependent and calcium-independent NOS activities in each particulate and soluble fraction of kidney by conversion of L-[3H]arginine to L-[3H]citrulline. Systolic blood pressure was elevated significantly (P < .001) in salt-sensitive but not salt-resistant rats. Calcium-dependent NOS activity in the soluble fraction was significantly lower in salt-sensitive rats than in salt-resistant rats (25.8 +/- 9.0 versus 48.2 +/- 19.2 disintegrations per microgram protein, respectively; P < .01). There were no differences in calcium-dependent NOS activity in the particulate fraction and calcium-independent NOS activity in the soluble fraction between groups. Renal norepinephrine content was lower in salt-sensitive rats than in salt-resistant rats (P < .05) and was positively correlated with calcium-dependent NOS activity in the soluble fraction (P < .01). Although no differences in endothelial and inducible-type NOS activity were observed a significant reduction in calcium-dependent NOS activity in the soluble fraction of the kidney of salt-sensitive rats suggests that the decreased neural-type NOS activity may in part be involved in the mechanism of salt-sensitive hypertension, possibly through alterations in renal sympathetic nervous activity and sodium handling.
D000818:Animals; D001794:Blood Pressure; D002118:Calcium / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D003627:Data Interpretation, Statistical; D006973:Hypertension / Q000209:etiology*; D007527:Isoenzymes / Q000032:analysis / Q000378:metabolism*; D007668:Kidney / Q000737:chemistry / Q000201:enzymology* / Q000378:metabolism; D008297:Male; D019001:Nitric Oxide Synthase / Q000032:analysis / Q000378:metabolism*; D009638:Norepinephrine / Q000032:analysis; D051381:Rats; D011919:Rats, Inbred Strains; D012588:Scintillation Counting; D012965:Sodium Chloride / Q000378:metabolism
D007527:Isoenzymes; D012965:Sodium Chloride; D019001:Nitric Oxide Synthase; D002118:Calcium; D009638:Norepinephrine