Influence of the calcium and vitamin D endocrine system on the "priming" of the liver for compensatory growth.
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.
Ethier
C
C
Centre de recherche clinique André-Viallet, Hôpital Saint-Luc, Montreal, Canada.
Goupil
D
D
Gascon-Barré
M
M
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
D004044:Dietary Proteins; D014807:Vitamin D; D004815:Epidermal Growth Factor; D004247:DNA; D066246:ErbB Receptors; D002117:Calcitriol; D002118:Calcium; D013936:Thymidine