Anticipated Results. Summary of Expected Results in the Proposed Studies: On high salt diet, IRS-1 and/or -2 mRNA and protein levels will be diminished in Dahl S versus R rats. No changes are anticipated in IRS-1 and/or -2 mRNA and protein levels in Dahl S rats on normal salt diet, or in Dahl R rats on any of the dietary treatments (low, normal and high salt diet). On low salt diet, IRS-1 and/or -2 mRNA and protein levels in Dahl S rats might not change or on the contrary they might increase because of the reduced levels of sodium acting on the salt-response element in the promoter region of IRS-1 and/or -2. It is postulated in the present hypothesis that this salt-responsive element possesses an inhibitory effect on IRS-1 and/or -2. The less salt the greater the IRS-1 and/or -2 mRNA and protein levels. Serine phosphorylation is expected to be enhanced in Dahl S versus R rats, possibly by the higher insulin levels in Dahl S rats.