Evidence for a difference in vitamin D metabolism between spontaneously hypertensive and Wistar-Kyoto rats.

Abstract

SUMMARY It has been contended that the metabolism of vitamin D in spontaneously hypertensive rats (SHR) is different from that in Wistar-Kyoto rats (WKY). To investigate this possibility, the plasma concentration of 1, 25-dihydroxycholecalciferol (1,25[OH] 2 D) and several known determinants of its production rate were measured in SHR and WKY given normal and restricted amounts of dietary phosphorus. In 12-week-old male SHR given a normal amount of dietary phosphorus, the mean plasma concentration of 1,25(OH) 2 D (72 ± 5 pg/ml) was significantly lower than that in agematched WKY (129 ± 6 pg/ml; p< 0.001). The lower plasma concentration of 1,25(OH) 2 D in the SHR could not be attributed to higher circulating levels of inorganic phosphorus or ionized calcium, lower plasma concentrations of 25-hydroxycholecalciferol, or acidosis. However, in the SHR, urinary excretion of cyclic adenosine 3',5'-monophosphate (12.5 ± 0.4 nmol/mg creatinine) was significantly lower than that in WKY (15.2 ± 0.3 nmol/mg creatinine; p<0.001). In both SHR and WKY, restriction of dietary phosphorus for 1 week induced an increase in the plasma concentration of 1,25(OH) 2 D without affecting blood pressure. The current findings Indicate that in 12-week-old male SHR, 1,25(OH) 2 D metabolism is different from that in age-matched WKY. The activity of 25-hydroxyvitamin D-la-hydroxylase, however, appears to be at least partially responsive to short-term restriction of dietary phosphorus. In SHR, the activity of 25-hydroxyvitamin D-la-hydroxylase may be lower than that hi WKY, perhaps due in part to some impairment in the renal metabolism of, or responsiveness to, cyclic adenosine 3,5'-monophosphate. (Hypertension 8: 1015(Hypertension 8: -1020(Hypertension 8: , 1986 KEY WORDS • 1,25-dihydroxycholecalciferol • hypertension • spontaneously hypertensive rats • phosphorus I N spontaneously hypertensive rats (SHR), the metabolism of calcium is different from that in Wistar-Kyoto rats (WKY), the most commonly used control. In SHR, increased urinary excretion of calcium, decreased serum or blood concentrations of ionized calcium, and increased serum concentrations of parathyroid hormone (PTH) have been reported. '~* In Received February 21, 1986; accepted June 16, 1986. support of their statement that SHR "represent a naturally occurring model of disturbed vitamin D metabolism," Lucas et al. 3 recently reported that in 12-week-old SHR, the mean serum concentration of 1, 25-dihydroxycholecalciferol (1,25[OH] 2 D) was lower than that in age-matched WKY. This difference, however, has not been found by other investigators in 10-to 15-week-old SHR and W K Y .4 6 7 In most of the previous studies in SHR and WKY, major determinants of 1,25(OH) 2 D production were not evaluated systematically in the same animals in which plasma levels of 1,25(OH) 2 D were measured. In the current study, we simultaneously measured plasma levels of 1,25(OH) 2 D and major determinants of 1,25(OH) 2 D production in 12-week-old SHR and WKY. To investigate the responses of SHR an...

High dietary cholecalciferol increases plasma 25-hydroxycholecalciferol concentration, but does not attenuate the hypertension of Dahl salt-sensitive rats fed a high salt diet

“…This study indicates that five times the standard cholecalciferol intake is sufficient to compensate for 25-OHD 3 loss when rats are fed 3% salt (three-times the standard salt intake) for 28 days. Spontaneously hypertensive rats have normal plasma 25-OHD concentrations [3,35,36], so decreased plasma 25-OHD concentration may be specific to salt-induced hypertension. Studies on humans have indicated an inverse relationship between plasma 25-OHD concentration or UVB light exposure and blood pressure [14,37].…”

Calcitropic hormones, platelet calcium, and blood pressure in essential hypertension.

“…- 43 The reason for these discrepancies in hypertensive humans is unclear but may relate to dietary or age differences of the subject groups between studies. Our results support the observations of elevated 1,25(OH) 2 D 3 in some older populations of essential hypertensive men.…”

Calcium transport and vitamin D in three breeds of spontaneously hypertensive rats.

“…8 The 25-OH-D concentration decreased with the feeding of a low calcium diet in both strains, but remained greater in SHR than in WKY. 8 In studies by others, 25-OH-D was found to be elevated 20 or the same 1 0 2 1 2 2 in the SHR as compared with the WKY. Thus, the findings of the present study with animals from different breeders reflect these published data: 25-OH-D concentration is dependent on breeder and age of animal.…”