Effect of inhibition of Na, K-ATPase on cytosolic free sodium and calcium in platelets of spontaneously hypertensive rats.
Cytosolic free sodium concentrations ([Na+]i) in intact platelets of 18 spontaneously hypertensive rats (SHR) and of 18 age-matched normotensive Wistar-Kyoto rats (WKY) were measured using the sodium-sensitive fluorescent dye sodium-binding-benzofuran-isophthalate. In resting platelets [Na+]i tended to be higher in SHR compared to WKY (20.5 +/- 3.5 mmol/L v 15.1 +/- 1.9 mmol/L, mean +/- SEM), but the differences were not statistically significant. Stimulation of the Na-H-exchange by 1.0 U/mL thrombin increased [Na+]i in SHR by 22.9 +/- 4.3 mmol/L and in WKY by 35.0 +/- 5.6 mmol/L in a similar way. After inhibition of Na, K-ATPase by 1 mmol/L ouabain there was a significant rise of [Na+]i both in platelets of SHR to 38.0 +/- 5.1 mmol/L (P < .01 compared to resting platelets) and in platelets of WKY to 26.5 +/- 4.3 mmol/L (P < .01). However, no significant difference could be observed between these two groups. Using the calcium-sensitive dye fura-2, resting cytosolic free calcium concentrations ([Ca2+]i) were found to be significantly higher in platelets of SHR compared to WKY (171.9 +/- 21.5 nmol/L v 93.14 +/- 19.7 nmol/L, P < .05). After the addition of ouabain [Ca2+]i was significantly higher in SHR compared to WKY (245.5 +/- 32.6 nmol/L v 159.6 +/- 22.5 nmol/L, P < .05). The results do not support the hypothesis that altered sodium-calcium exchange causes elevated cytosolic free calcium in SHR.
Tepel
M
M
Medizinische Universität-Poliklinik, Universität Münster, Germany.
Husseini
S
S
Wischniowski
H
H
Zidek
W
W
D000818:Animals; D001792:Blood Platelets / Q000378:metabolism*; D002118:Calcium / Q000097:blood*; D003600:Cytosol / Q000378:metabolism*; D016257:Fura-2; D006973:Hypertension / Q000097:blood / Q000378:metabolism*; D009994:Osmolar Concentration; D010042:Ouabain / Q000494:pharmacology; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D012964:Sodium / Q000097:blood*; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors* / Q000097:blood; D013917:Thrombin / Q000494:pharmacology
D010042:Ouabain; D012964:Sodium; D013917:Thrombin; D000254:Sodium-Potassium-Exchanging ATPase; D002118:Calcium; D016257:Fura-2