Evidence of 1,25-dihydroxyvitamin D synthesis by the rat Walker carcinosarcoma 256

Acción de la 24,25(OH)2D3, 1,25(OH)2D3 y 25(OH)D3 sobre la actividad fosfatasa en calotas de feto de ratas

“…The actions attributed to 25(OH)D3 could be due to itself or to more polar vitamin D3 metabolite 1,25(OH)2D3 produced by a hydroxylation of 25(OH)D3 in the calvaria (7,30,31). However, the actions produced by 24,25(OH)2D3 at 10 -7 M on AP and TRAP activities in calvaria cultures differ from the actions found by 1,25(OH)2D3 and 25(0H)D3.…”

“…From these results it is possible to conclude that 1,25(OH)2D3 and 25(0H)D3 produce effects both at 10 minutes and 30 minutes. These findings ate in agreement with the authors who ascribe physiological actions for 1,25(OH)2D3 to an independent way of "genomic" mechanism (2,9,16,21,23,24), a finding which suggests that the 1,25(OH)2D3 actions could be independent of the de novo protein synthesis.The actions attributed to 25(OH)D3 could be due to itself or to more polar vitamin D3 metabolite 1,25(OH)2D3 produced by a hydroxylation of 25(OH)D3 in the calvaria (7,30,31). However, the actions produced by 24,25(OH)2D3 at 10 -7 M on AP and TRAP activities in calvaria cultures differ from the actions found by 1,25(OH)2D3 and 25(0H)D3.…”

Effects of Parathyroid Hormone Related Peptide (1 - 34) and 1,25-Dihydroxyvitamin D on Bone Alkaline Phosphatase Activity in Fetal Rat Calvaria Cultures

“…Moreover, W256 tumor homogenates display 25(OH)D-1 n-hydroxylase activity (Traba, Risco, Hurtado, de Miguel, Esbrit and Rapado 1990). In a previous study, we have shown that in spite of elevated serum calcium in tumor-bearing rats, renal la-hydroxylase activity was unchanged compared to that in control rats (Traba et al 1989).…”

“…One of the variants of Walker carcinosarcoma 256 (W256) in the rats is an experimental model of humorat hypercalcemia of malignancy (HHM) similar to that associated with a variety of human tumors (Mundy 1987;Minne, Rune, Bel!winkel and Ziegler 1975). The origin of hypercalcemia in HHM is not yet well established but a parathyroid hormone related peptide (PTHrP) and other osteolytic factors seem to be possible mediators for the HHM syndrome (Mundy 1987), On the other hand, high serum levels of 1,25-dihydroxyvitamin D I1,25(OH)2D] in W256 host rats have been reported (Scharla, Oswald, Blind, Sattar, Ziegler and Mirine 1987;Traba, Hurtado, Risco, Cuesta, Esbrit and Rapado 1989). Moreover, W256 tumor homogenates display 25(OH)D-1 n-hydroxylase activity (Traba, Risco, Hurtado, de Miguel, Esbrit and Rapado 1990).…”

“…The origin of hypercalcemia in HHM is not yet well established but a parathyroid hormone related peptide (PTHrP) and other osteolytic factors seem to be possible mediators for the HHM syndrome (Mundy 1987), On the other hand, high serum levels of 1,25-dihydroxyvitamin D I1,25(OH)2D] in W256 host rats have been reported (Scharla, Oswald, Blind, Sattar, Ziegler and Mirine 1987;Traba, Hurtado, Risco, Cuesta, Esbrit and Rapado 1989). Moreover, W256 tumor homogenates display 25(OH)D-1 n-hydroxylase activity (Traba, Risco, Hurtado, de Miguel, Esbrit and Rapado 1990). In a previous study, we have shown that in spite of elevated serum calcium in tumor-bearing rats, renal la-hydroxylase activity was unchanged compared to that in control rats (Traba et al 1989).…”