Energy turnover and mechanical properties of resting and contracting aortas and portal veins from normotensive and spontaneously hypertensive rats

Abstract

Aortas and portal veins from spontaneously hypertensive rats (SHR) and matched normotensive Wistar-Kyoto rats (WKY) were studied with respect to their energy turnover and mechanical properties. Relaxed aortas from SHR 16-17 weeks and 20-25 weeks of age were stiffer, had smaller circumference, and greater maximal active wall tension compared to WKY aortas. Active stress (force/area) was not different. Passive and active length-force relations of portal veins from 16 to 17-week-old SHR and WKY were not different. O2 consumption (J(O2)) and lactate production (J(LA)) were studied in aortas and portal veins from 20- to 25-week-old rats. In relaxed aortas, J(O2) was 0.63 ± 0.03 (n = 11) and 0.54 ± 0.03 (n = 10) μmol/min per g dry wt in SHR and WKY, respectively (P < 0.05). On activation by high-K+ solution, J(O2) increased with tension in a similar way in both groups. In contrast, J(LA), about 0.85 μmol/min per g, did not differ, and decreased with tension development. J(O2) of relaxed portal veins, about 1.5 μmol/min per g dry wt, and the increase in J(O2) with contraction were not different between SHR and WKY, but the J(O2)-active stress relation was steeper in spontaneous activity than in K(v)+ contractures. J(LA) was similar in SHR and WKY portal veins, about 1 μmol/min per g, and unlike behavior of the aortas, it increased with tension. Thus it is evident that SHR show increased arterial metabolism, which is not accounted for by an increased energy demand of the contractile system.