The activity of transport adenosine triphosphatases (ATPases) in saponin-treated erythrocytes as well as the passive membrane permeability for 86Rb+ (K+), 45Ca2+ uptake (in the presence of orthovanadate) and the rate of Na(+)-H+ exchange in intact erythrocytes were studied in spontaneously hypertensive rats (SHR), Wistar-Kyoto (WKY) and Brown-Norway (BN.lx) rats. Higher Na+,K(+)-ATPase activity, lower Ca(2+)-ATPase activity, increased passive K+ permeability and greater 45Ca2+ uptake were observed in erythrocytes from SHR compared with BN.lx rats. Similar differences in the last two parameters were also disclosed by a comparison of SHR and WKY rats. The rate of Na(+)-H+ exchange in SHR erythrocytes was greater than in WKY rats but equal to that of BN.lx rats. A genetic analysis did not reveal a significant correlation between Na(+)-H+ exchange rate and blood pressure in F2 SHR x WKY hybrids.