Cytosolic pH and calcium in Dahl salt-sensitive and salt-resistant rats: the relationship to plasma lipids.
OBJECTIVE
To search for alterations of cytosolic pH and cell calcium handling in platelets and erythrocytes of Dahl rats susceptible and resistant to salt-induced hypertension.


METHODS
Blood pressure, plasma lipids, platelet cytosolic calcium concentration ([Ca2+]i) and pH (pHi) together with thrombin-induced changes in these parameters as well as erythrocyte [Ca2+]i and 45Ca influx were determined in Dahl salt-sensitive (SS/Jr) and salt-resistant (SR/Jr) rats aged 9, 15 and 24 weeks, which were fed a low-salt diet (0.3% NaCl), and in animals fed high-salt diet (4% NaCl) for 5-10 weeks since weaning.


RESULTS
With a low salt intake platelet pHi was lower in SS/Jr than it was in SR/Jr rats, whereas basal platelet [Ca2+]i was similar in rats of both strains. The difference in basal pHi between SS/Jr and SR/Jr rats increased progressively with age of animals. A high salt intake from youth did not influence platelet [Ca2+]i in rats of either strain but it caused an earlier decrease in pHi in SR/Jr than it did in SS/Jr rats. Thrombin stimulation induced similar elevations of pHi and [Ca2+]i in rats of both strains, irrespective of age, salt intake and response of blood pressure to salt intake. Erythrocyte 45Ca influx and [Ca2+]i were greater for SS/Jr rats but only the latter parameter was correlated positively to blood pressure. Both regulation of platelet pHi and erythrocyte Ca2+ handling were significantly related to plasma lipid levels.


CONCLUSIONS
Platelets of SS/Jr rats fed a low-salt diet were characterized by a lower basal cytosolic pHi but unchanged [Ca2+]i relative to those of SR/Jr rats. Hypertension induced by high salt intake was associated with increased erythrocyte [Ca2+]i but not with elevation of platelet [Ca2+]i or alteration of response to stimulation with thrombin.
Zicha
J
J
Institute of Physiology, Czech Academy of Sciences, Prague, Czech Republic.
David-Dufilho
M
M
Kunes
J
J
Pernollet
M G
MG
Devynck
M A
MA
D000818:Animals; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D001794:Blood Pressure; D002118:Calcium / Q000378:metabolism*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D004912:Erythrocytes / Q000187:drug effects / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D006973:Hypertension / Q000097:blood* / Q000209:etiology / Q000503:physiopathology; D008055:Lipids / Q000097:blood*; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D017673:Sodium Chloride, Dietary
D008055:Lipids; D017673:Sodium Chloride, Dietary; D002118:Calcium