Reference

Biological activity of 1a,24-dihydroxyvitamin D3; a new synthetic analog of the hormonal form of vitamin D

Biological activity of 1a,24-dihydroxyvitamin D3; a new synthetic analog of the hormonal form of vitamin D. Kawashima, H.; Hoshina, K.; Ishizuka, S.; Hashimoto, Y.; Takeshita, T.; Ishimoto, S.; Noguchi, T.; Ikekawa, N.; Morisaki, M.; Orimo, H. (Teijin Inst. Bio-med. Res., Hino, Japan). Vitam. D: Biochem., Chem. Clin. Aspects Relat. Calcium Metab., Proc. Workshop Vitam. D, 3rd, 143-5. Edited by: Norman, Anthony W.; Schaefer, K.; Coburn, J. W. de Gruyter: Berlin, Ger. (English) 1977. CODEN: 36PEA2. DOCUMENT TYPE: Conference CA Section: 1 (Pharmacodynamics) Section cross-reference(s): 2, 18 1a,24(R)-dihydroxyvitamin D3 (I) [57333-96-7] and 1a,24(S)-dihydroxyvitamin D3 [57333-95-6] stimulated intestinal Ca transport and bone Ca mobilization in vitamin D-deficient rats. The stereoisomers were also effective in treating rickets in rats. I had a longer duration of action and was more potent in curing rickets than was 1a,24(S)-dihydroxyvitamin D3. After the i.v. administration of I-3H, labeled 1a,24(R),25-trihydroxyvitamin D3 [56142-94-0] was isolated from the plasma and liver.

Inhibitory effects of active vitamin D preparations on PTH secretion in rats

Inhibitory effects of active vitamin D preparations on PTH secretion in rats. Kugai, Nobuo; Koide, Yoshinobu; Kimura, Satoshi; Yamashita, Kamejiro (Inst. Clin. Med., Univ. Tsukuba, Sakura 305, Japan). Endocrinol. Jpn., 31(2), 151-8 (English) 1984. CODEN: ECJPAE. ISSN: 0013-7219. DOCUMENT TYPE: Journal CA Section: 2 (Mammalian Hormones) To study the effects of various vitamin D prepns. on parathormone (PTH) [9002-64-6] secretion, serum Ca and urinary excretion of cAMP [60-92-4] were monitored in conscious perfused rats, and the influences of bolus i.v. injections of the prepns. on these parameters were examd. Three hours after the administration of 0.25 mg/kg (0.6 nmol/kg) of 1a,24(R)-dihydroxycholecalciferol [1a,24(OH)2D3] [57333-96-7], the urinary excretion of cAMP decreased to a level compatible with that of parathyroidectomized (PTX) rats (50% of initial value) with no change in the concn. of serum Ca2+ (total and ionized). In PTX rats supplemented with bovine PTH (1 U/h), the vitamin D prepn. showed no significant effects either on the urinary excretion of cAMP or on serum Ca. These effects were rather specific for active vitamin D prepns., i.e. 1,25-dihydroxyvitamin D3 (1a,25(OH)2D3) [32222-06-3] (0.25 mg/kg) and 1a-hydroxyvitamin D3 (1aOHD3) [41294-56-8] (1.25-6.25 mg/kg). However, 24(R),25-dihydroxyvitamin D3 (24,25(OH)2D3) [55721-11-4] (up to 25 mg/kg) had no significant effect on these parameters. In rats, active vitamin D prepns. appear to specifically inhibit PTH secretion without causing a significant increase in the serum Ca2+ concn., reflecting a direct feedback mechanism between active vitamin D metabolite and the parathyroid glands.