Different mechanisms of modulation of gap junction communication by non-genotoxic carcinogens in rat liver in vivo

This is a comparative study of the mechanisms by which three different rodent non-genotoxic carcinogens modulate connexin-mediated gap junction intercellular communication in male rat liver in vivo. In the case of the peroxisome proliferating agent Wy-14,643, a non-hepatotoxic dose of 50mg/kg led to a marked loss of inter-hepatocyte dye transfer associated with a loss of both Cx32 and Cx26 protein expression. In contrast, p,p'-dichlorodiphenyltrichloroethane (DDT) at a non-hepatotoxic dose (25mg/kg) was not found to alter Cx32 or Cx26 expression or to produce a measurable Cx32 serine phosphorylation but did give a small, significant reduction of cell communication. Carbon tetrachloride (CCl(4)) did not affect cell communication (despite a small significant reduction of Cx32 content) at a non-hepatotoxic dose. Both loss of communication and Cx32 expression was observed only at a dose that caused hepatocyte toxicity as evidenced by increased serum alanine aminotransferase activity. Overall, the findings emphasise that loss of gap junctional communication in vivo can contribute to carcinogenesis by non-genotoxic carcinogens through different primary mechanism. In contrast to Wy-14,643 and DDT, the results with CCl(4) are consistent with a requirement for hepatotoxicity in its carcinogenic action.

Glycerol intolerance in a child with intermittent hypoglycemia

A 3-yr-old boy was investigated for numerous episodes of fatigue, irritability, pallor, and sweating, which began at 11 mo of age, when he had an episode of symptomatic hypoglycemia with ketonuria. He had euphoria, mental confusion, drowsiness, nausea, and vomiting 1-5 hr after oral administration of glycerol in doses of 0.5-1.0gm/kg. Orally administered MCT (1 gm/kg) had similar effects. On one occasion, oral glycerol also provoked hypoglycemia, as had a 16 1/2 hr fast. Intravenously administered glycerol (0.09 gm/kg) induced an immediate loss of consciousness from which he recovered spontaneously after 30 min; there were no changes in blood glucose values. Intravenously administered fructose (0.25 gm/kg) was tolerated normally. Leukocytes showed normal activities for FDPase, glycerol kinase, and glycerol phosphate dehydrogenase. The restriction of dietary intake of fat has been associated with a marked improvement in physical and mental activities. These observations suggest a unique, yet undifined intolerance to glycerol, which suggest caution in the diagnostic use of glycerol in the investigation of hypoglycemia as well as in the therapy of increased intracranial or intraocular pressure.