Carrier‐mediated transport controls hydroxyproline catabolism in heart mitochondria from spontaneously hypertensive rat

Abstract

In this study we have investigated hydroxyproline transport in rat heart mitochondria and, in particular, in heart left ventricle mitochondria isolated from both spontaneously hypertensive and Wistar-Kyoto rats. Hydroxyproline uptake by mitochondria, where its catabolism takes place, occurs via a carrier-mediated process as demonstrated by the occurrence of both saturation kinetics and the inhibition shown by phenylsuccinate and the thiol reagent mersalyl. In any case, hydroxyproline transport was found to limit the rate of mitochondrial hydroxyproline catabolism. A significant change in Vmax and Km values was found in mitochondria from hypertensive/hypertrophied rats in which the Km value decreases and the Vma x value increases with respect to normotensive rats, thus accounting for the increase of hydroxyproline metabolism due to its increased concentration in a hypertrophic/hypertensive state.Key words': Hypertension; Hydroxyproline; Mitochondria; Transport; Collagen major determinant of its architecture, structural integrity and mechanical properties [8].In this paper, we first show HYP carrier-mediated uptake in rat heart mitochondria, after which investigation is made of HYP transport in left ventricle mitochondria in a study carried out with spontaneously hypertensive rats and normotensive Wistar-Kyoto rats, both at 5 and 24 weeks of age. This is worthy of special attention since both the collagen concentration and the total amount of hydroxyproline content in the left ventricle were found to increase in spontaneously hypertensive rats as a result of increased fibroblastic activity in the pathogenesis of cardiac hypertrophy [8]. An increase in HYP translocator activity in hypertrophy/hypertension was shown. In all animals investigated, HYP transport across the mitochondrial membrane was found to limit the HYP oxidation rate. Materials and methods

Aspartate transporter expression and activity in hypertrophic rat heart and ischaemia–reperfusion injury

“…). Cardiac hypertrophy in the SHR was confirmed by the significantly greater ventricle weight (1389 ± 28 mg SHR versus 1151 ± 29 mg WKY, P > 0.001, t test, n = 69) and significantly greater ventricular mass index (0.599 ± 0.03 WKY versus 0.738 ± 0.03 SHR, P < 0.02, t test, n = 69), with these values consistent with previous reports about WKY and SHR (Doggrell & Brown, 1998; Atlante et al 1996).…”

“…Hearts were obtained from two strains of male rats, namely the spontaneous hypertensive rat (SHR) and their corresponding normotensive control, the Wistar Kyoto (WKY) (Doggrell & Brown, 1998; Atlante et al 1996). The rats were age matched at 18 ± 3 weeks old, which was chosen to coincide with reports documenting the development of myocardial hypertrophy in the SHR (Atlante et al 1996; Doggrell & Brown, 1998). The rats were also weight matched at 354.7 ± 3.8 g WKY versus 349.2 ± 3.1 g SHR ( n = 69, all values are means ± s.e.m.…”

Metabolism of [13C5]hydroxyproline in vitro and in vivo: implications for primary hyperoxaluria

“…It is possible that the method we used lacked sufficient sensitivity to detect low levels of HPOX expression in some of these tissues or that there are differences in mRNA stability. Rat heart mitochondria, for instance, have been reported to metabolize Hyp, with a resultant reduction of NAD ϩ , indicating that, in this species, heart tissue most likely expresses HPOX activity as well as 1P5CDH (4).…”

“…The remaining chloride was exchanged with formate by dissolution of the Hyp in 4 ml of deionized water and passage through a 1 ϫ 30 cm formate-form AG1 X8 column (Bio-Rad) with deionized water as the mobile phase. The sodium in the Hyp was exchanged for NH 4 ϩ by adjustment of the pH to Ͼ12 with 12.7 M ultrapure NaOH and passage through a 1 ϫ 30 cm NH 4 ϩ -form AG 50W-X8 column with deionized water used as the mobile phase.…”