Nuclear DNA content of altered hepatic foci in a rat liver carcinogenesis model.

In individual altered hepatic foci (AHF), aneuploidy occurs before malignant changes can be diagnosed histologically (O. Sudilovsky and T. K. Hei. Fed. Proc., 42:2225, 1983). In the current experiments Sprague-Dawley rats of both sexes were given i.p. injections of diethylnitrosamine (50 mg/kg body weight) 18 h after partial hepatectomy and were given a choline-sufficient diet (CS) for 1 wk. Four treatment groups were then formed and fed CS, CS containing 0.05% phenobarbital (PHB), choline-deficient diet (CD), and CD with 0.05% PHB. An extra female group received infusions of saline after the hepatectomy and fared CD. Control animals were partially hepatectomized, inoculated i.p. with saline, and placed on CS. The rats were sacrificed 16 wk later, liver sections were stained with a combined Feulgen-gamma-glutamyl transpeptidase stain, and the DNA content of gamma-glutamyl transpeptidase-positive foci was measured cytospectrophotometrically. There were no AHF in the control animals. Hepatocytes from control livers and cells adjacent to foci in treated livers had peaks corresponding to the 2C, 4C, and 8C range. In AHF the ploidy, however, was predominantly diploid, tetraploid, or heterogeneous. The ratio of diploid to tetraploid cells in foci of rats provided with CS + PHB was 5.5 and in those supplied with CD + PHB was 0.09. This suggested that dietary manipulations change the nuclear DNA distribution of AHF. Aneuploidy was also present, as expected, in 4 of 33 AHF in the animals placed on CD + PHB. It was observed as well in 2 of 26 AHF of rats given CD but in none of the 20 AHF fed CS + PHB. These data indicate that CD (which acts as both initiator and promoter) may be responsible for the appearance of aneuploidy. A general model, based on these results and the clonality of each individual focus, is proposed for the development of cells through the preneoplastic stage.

Lovastatin enhances in vitro radiation-induced apoptosis of rat B-cell lymphoma cells.

Our previous demonstration of an antimetastatic effect of lovastatin, both in rat sarcoma and lymphoma tumor-models, as well as the fact that lovastatin and radiation are able to stop the cell cycle in different phases, suggested the feasibility of a combined treatment. We studied the effect of the in vitro combined treatment of a B-cell rat lymphoma (L-TACB) with lovastatin and irradiation. The results herein obtained provide new information about the role of statins as radiosensitizers. The antitumor effect of the combined treatment was higher than that elicited by either treatment alone. This effect could be a consequence, at least in part, of an enhanced apoptosis.

Is 8-hydroxydeoxyguanosine a mediator of carcinogenesis by a choline-devoid diet in the rat liver?

The mechanism(s) by which a diet devoid of choline (CD) induces hepatocellular carcinomas in rats remains unknown. Although animals fed this diet develop nuclear lipid peroxidation, suggesting oxidative DNA damage, there is no direct evidence that this occurs. In this study, 8-hydroxydeoxyguanosine (8-OHdG), a DNA adduct generated by reactive oxygen species, was analyzed in the liver of rats fed a CD diet and in controls receiving a choline-sufficient (CS) diet. After partial hepatectomy, the animals were injected with diethylnitrosamine (DEN, 50 mg/kg body wt) or with saline and fed a CD or CS diet for 24 weeks. While liver DNA from rats injected either with DEN or saline and fed a CS diet did not show detectable amounts of the nucleotide, those who were fed DEN/CD and saline/CD demonstrated similar, easily measurable levels of 8-OHdG. These results indicate that there is a positive association between the continuous administration of a CD diet and the production of 8-OHdG in liver DNA, and support the idea that oxidative DNA damage is involved in carcinogenesis by a CD diet.

Maternal effects on the phenotypic expression of the skeletal store of calcium (bone mass) and related variables in the rat.

The phenotypic expression of bone mass and several related variables were investigated in the rat, assessing the differences and resemblances between two strains of inbred rats and their reciprocal hybrids. The data obtained indicated a strong influence of the maternal environment in the expression of total calcium mass and the rates of true calcium (Ca) absorption, endogenous fecal Ca excretion and bone Ca accretion. The simultaneous occurrence of maternal effects on characters obviously related, suggested that formation and maintenance of bone mass is accomplished by a series of specialized cellular functions, possibly regulated by a single genetic block. Maternal effects on bone mass and related variables appear to be determined in utero and are fully expressed at adulthood.

Genetic conditioning of the response of rat bone tissue to estradiol.

The effects of the administration of pharmacological doses of estradiol were studied in two genetically different lines of inbred rats, at two stages of development, to gain a new insight into the genetic and physiological organization of the response of bone and Ca metabolism to exogenous estrogens. The comparative analysis of the effects on bone tissue revealed that the pattern of cellular activities at bone surfaces, the increased trabecular bone volume and the increased calcium accretion are separate responses. Likewise, the closure of the epiphyseal plate may not be associated with the curtailment of body weight increase. In addition, only one of the lines increased its intestinal calcium absorption. It appears evident that the response to exogenous estradiol relies upon the action of more than one locus. The simultaneous occurrence of partial responses (successful treatment) depends upon as yet undefined genetic and environmental (endocrine, nutritional, etc.) conditions. Extension of these conclusions to the human being implicates the recognition that a fraction of the patients undergoing estrogenic treatment may be insensitive to therapy.

Differential responses of two inbred rat strains to a choline-deficient diet during liver carcinogenesis.

We examined the effect of a choline-devoid (CD) diet on the development of gamma-glutamyltranspeptidase (GGT)-positive foci in both sexes of the inbred rat strains Fischer 344 and PVG/R8. Following partial hepatectomy, 7 to 8 week old animals were given a choline-supplemented diet for 1 week. Two groups were then formed: one remained on choline-supplemented diet as control, and the other was switched to the CD diet. The animals were killed 10, 16 and 24 weeks later. Liver samples were then stained with hematoxylin-eosin and Masson's trichromic, and histochemically analyzed for GGT. Fatty degeneration and collagen formation was severe in F344 males while it was mild or absent in F344 females and in both sexes of PVG rats. Stereochemical quantitation showed that F344 males had a significantly greater increase in the number of positive liver foci (as well as in their mean volume and the percentage of liver occupied by them) than F344 females and PVG animals of either sex (P < 0.01). These results suggest that not only sex but also the genotype of the host plays a role in the different responses to a CD diet. In depth analysis of these factors should prove valuable to investigate this dietary model of hepatocarcinogenesis further.

Non uniform effect of estradiol on the rat skeleton.

Pharmacological doses of estradiol administered to rats increased the Ca mass of their femurs through a significant reduction in the rate of Ca resorption. On a body basis, the same animals showed increased rates of skeletal Ca deposition and resorption and no effect on the skeletal mass. The non uniform effect of estradiol on the skeleton, if confirmed in the human being, may limit the applicability of estrogenic treatment.