title: Influence of the calcium and vitamin D endocrine system on the "priming" of the liver for compensatory growth.
abstract: The liver is known to be sensitive to dietary challenge and to reduction in its functional mass. To investigate the influence of the vitamin D endocrine system on the hepatic growth response, liver DNA synthesis (S phase of cell cycle) was primed by dietary manipulation (high carbohydrate/protein-free diet x 3 d followed by high protein diet x 15-18 hr) in animals presenting various calcium and vitamin D status. Data indicate the dietary manipulation increased [3H]thymidine incorporation into DNA following vitamin D3 (D3) or 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) administration (p less than 0.0001) while vitamin D depleted (D-) rats (both hypo and normocalcemic) showed no significant increases over unchallenged rats (p less than 0.0001). Studies on the hepatic EGF receptor indicate that while no significant between-group difference was observed in receptor density or affinity, evaluation of the receptor density in relation to the [3H]thymidine incorporation response revealed a higher receptor density in responders (D3 and 1,25(OH)2D3 supplemented groups) with 30.2 +/- 1.4% maximum binding than in non-responders (hypo and normocalcemic D- groups) with 25.4 +/- 1.8% maximum EGF binding (p less than 0.03); EGF EC50 was found to be 50.2 +/- 4.4 and 63.8 +/- 9.7 ng/ml in responders and non-responders respectively (p = 0.1). These data indicate that vitamin D depletion is accompanied by hyporesponsiveness when challenged by a dietary protocol known to prime the liver for growth inducing stimuli.
authors.affiliation: Centre de recherche clinique André-Viallet, Hôpital Saint-Luc, Montreal, Canada.
authors.forename: C
authors.initials: C
authors.lastname: Ethier
authors.forename: D
authors.initials: D
authors.lastname: Goupil
authors.forename: M
authors.initials: M
authors.lastname: Gascon-Barré
mesh_terms: D000818:Animals; D002117:Calcitriol / Q000494:pharmacology*; D002118:Calcium / Q000494:pharmacology*; D004247:DNA / Q000096:biosynthesis; D004044:Dietary Proteins / Q000494:pharmacology*; D004815:Epidermal Growth Factor / Q000378:metabolism; D066246:ErbB Receptors / Q000378:metabolism; D005260:Female; D006498:Hepatectomy; D008099:Liver / Q000502:physiology; D008115:Liver Regeneration / Q000502:physiology*; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D013936:Thymidine / Q000378:metabolism; D014807:Vitamin D / Q000494:pharmacology*; D014808:Vitamin D Deficiency / Q000378:metabolism
chemical_list: D004044:Dietary Proteins; D014807:Vitamin D; D004815:Epidermal Growth Factor; D004247:DNA; D066246:ErbB Receptors; D002117:Calcitriol; D002118:Calcium; D013936:Thymidine