Percutaneous and oral absorption of chlorinated paraffins in the rat

Parallel percutaneous absorption studies of two 14C-labelled chlorinated paraffins (C18, 50-53% chlorination; C28, 47% chlorination) were carried out in the Sprague-Dawley rat. The dermally applied dose (66 mg/cm2) was approximately equivalent to 2.0 g/kg of body weight. An oral absorption study with the C18-chlorinated paraffin (0.5 g/kg) was carried out in rats for comparison. Less than 1% of the dermally applied dose of [1-14C]polychlorooctadecane (50-53% chlorination) and less than 0.1% of the applied dose of [14,15-14C]polychlorooctacosane (47% chlorination) were recovered in excreta, expired air and tissues after 96 hours. In contrast, approximately 86% of the orally administered dose of [1-14C]polychlorooctadecane (0.5 g/kg) was recovered. These results indicate that rat skin acts as an effective barrier to chlorinated paraffins containing eighteen or more carbons and more than 40% chlorine by weight. The oral absorption of the C18 chlorinated paraffin can be estimated to be nearly 100 times greater than its dermal absorption. Based on current toxicity results from rodent experiments and these present findings, chlorinated paraffins of the type tested would be expected to have little or no effect in animals as a result of dermal exposure. It is reasonable to assume that such chlorinated paraffins are unlikely to be systemically toxic to humans by skin contact under normal conditions of production and use.

Percutaneous absorption of benzo[a]pyrene in the rat: comparison of in vivo and in vitro results

Percutaneous absorption of 14C-labeled benzo[a]pyrene (BaP) was studied in five-day in vivo and in vitro experiments with female Sprague-Dawley rats following single topical doses of 9-10 micrograms/cm2. The in vivo percutaneous absorption was measured by the presence of 14C radioactivity in urine, feces and tissues. In vitro percutaneous absorption was measured with excised (non-viable) skin in Franz-type diffusion cells. Several modifications of standard diffusion cell techniques which are known to enhance the transport of lipophilic compounds were evaluated. In vitro penetration was determined by directly measuring the level of 14C radioactivity in the receptor fluid. BaP was observed to readily penetrate in vivo with a total of 46.2% (n = 4, SD = 3.4%) of the applied dose being absorbed over five days. In in vitro experiments using an approximately 350 micronthick skin section and normal saline receptor solution, only 2.1% of the applied BaP diffused into the receptor fluid over five days. In in vitro experiments using full-thickness skin and a 6% solution of nonionic surfactant receptor fluid, 28.0% of the applied BaP diffused into the receptor fluid over five days. When both an approximately 350 microns-thick skin section and a 6% surfactant receptor solution were used in vitro, 49.9% (n = 4, SD = 3.1%) of the BaP dose was found in the receptor fluid after five days. The results show that the modified in vitro method is suitable for studying percutaneous absorption of lipophilic compounds such as BaP.

Percutaneous absorption of anthracene in the rat: comparison of in vivo and in vitro results

The present study was conducted to evaluate the applicability of in vitro percutaneous absorption techniques to estimate in vivo absorption of polynuclear aromatic (PNA) compounds commonly found in mineral oils. The percutaneous absorption of 14C-labeled anthracene, a three-ring PNA, was compared in a six-day in vivo and in vitro experiment with female Sprague-Dawley rats following a single topical dose (9.3 micrograms/cm2). In vivo absorption was measured by the presence of 14C radioactivity in urine, feces and tissues and in vitro absorption by penetration of radioactivity through excised skin into the receptor fluid of Franz-type diffusion cells. Several modifications of standard diffusion cell techniques were used which are known to enhance the absorption of lipophilic compounds. Anthracene was observed to readily penetrate the skin in both experiments and the total amounts absorbed in vivo and in vitro were seen to gradually coalesce over time. Within six days after application, 52.3 and 55.9% of the administered anthracene was absorbed in vivo and in vitro, respectively.

Percutaneous absorption of anthracene in the rat: comparison of in vivo and in vitro results

The present study was conducted to evaluate the applicability of in vitro percutaneous absorption techniques to estimate in vivo absorption of polynuclear aromatic (PNA) compounds commonly found in mineral oils. The percutaneous absorption of 14C-labeled anthracene, a three-ring PNA, was compared in a six-day in vivo and in vitro experiment with female Sprague-Dawley rats following a single topical dose (9.3 micrograms/cm2). In vivo absorption was measured by the presence of 14C radioactivity in urine, feces and tissues and in vitro absorption by penetration of radioactivity through excised skin into the receptor fluid of Franz-type diffusion cells. Several modifications of standard diffusion cell techniques were used which are known to enhance the absorption of lipophilic compounds. Anthracene was observed to readily penetrate the skin in both experiments and the total amounts absorbed in vivo and in vivo were seen to gradually coalesce over time. Within six days after application, 52.3 and 55.9% of the administered anthracene was absorbed in vivo and in vitro, respectively.

Effects of adriamycin on enzymes of adenine nucleotide metabolism in heart cell cultures

Effects of adriamycin (ADM) treatment on rat heart cells in culture were examined. ADM treatment (lug/ml) for 3 hr, 48 to 51hr of culture age, had no effect on oxygen consumption, myosin content or myosin ATPase activity. In contrast, the activities of creatine kinase, adenylate kinase and adenosine deaminase were significantly lower in ADM-treated cells than in corresponding controls at 72 and 96 hr of culture age. Fall in the activities of these key enzymes of adenine nucleotide metabolism would lead to disturbances in energy metabolism, and results in the functional impairment of heart cells.

Oxygen consumption of mammalian myocardial cells in culture: measurements in beating cells attached to the substrate of the culture dish

A Lucite attachment which permitted the measurement of oxygen consumption in cells in culture without manipulating the cells was constructed. The attachment fit over commercially available dishes for cell culture and had an oxygen electrode built into it. Oxygen uptake of cells in culture was thus measured. Cells were attached to the substrate of the culture dish during the measurements and could be observed in an inverted phase microscope. Cells did not show any morphological changes, e.g., cell shapes or beating rate in case of myocardial cells, before and after the measurements of oxygen consumption. Using this method the rate of oxygen consumption was determined in rat myocardial and heart non-muscle cells in culture and also in HeLa and L6 cell lines. Myocardial cells in culture had an approximately four times higher rate of oxygen uptake compared with heart non-muscle, HeLa, and L6 cells. The oxygen uptake of beating myocardial cells was higher by about 50% compared with quiescent myocardial cells.

Isozymes of creatine kinase in mammalian cell cultures

Previous studies on the energy metabolism of rat myocardial cells in culture supported the hypothesis that the creatine-phosphocreatine-creatine kinase system plays an important role in the intracellular transport of energy from the mitochondria to the myofibrils and in the regulation of energy production coupled to energy utilization in this model system. Effective functional compartmentation of ATP could result from the binding of creatine kinase to cellular organelles (e.g., myofibrils and mitochondria) such that high energy charge at the myofibrils is maintained by the reverse creatine kinase reaction, while phosphocreatine is synthesized mainly at the mitochondria in the forward creatine kinase reaction. It was, therefore, essential to demonstrate the presence of mitochondrial creatine kinase in the cultured myocardial cells to support this hypothesis, particularly since the mitochondrial creatine kinase was reportedly absent in fetal hearts. Using electrophoresis on cellulose acetate strips, the mitochondrial creatine kinase isozyme, as well as MM, MB, and BB isozymes, have now been demonstrated in myocardial cultures derived from neonatal rats. The mitochondrial creatine kinase increased with age in culture and with age of animal from which the culture is derived. Furthermore, the addition of creatine to culture media stimulates its synthesis. The mitochondrial creatine kinase isozyme was not detected in nonmuscle cells in culture derived from the neonatal rat hearts, nor in L6 muscle cell line. Phosphocreatine was present in all cells, but the regulation of energy metabolism and energy shuttle by creatine-phosphocreatine-creatine kinase could be operative only in the cells where the mitochondrial creatine kinase is present. This regulatory mechanism provides for an efficient system concomitant with the continuous energy demand of the myocardium; it is not ubiquitous and its development in myocardial cells seems to be triggered postnatally.

Mitochondrial creatine kinase in mammalian myocardial cells in culture

Previous studies on the energy metabolism of rat myocardial cells in culture supported the hypothesis that the creatine-phosphorylcreatine-creatine kinase system is essential for intracellular transport of energy from the mitochondria to the myofibrils and in the regulation of energy production to meet energy utilization. Effective functional compartmentation of ATP could result from the binding of creatine kinase to cellular organelles (e.g., myofibrils and mitochondria) so that the high-energy charge at the myofibrils is maintained by the reverse creatine kinase reaction, whereas phosphorylcreatine is synthesized mainly at the mitochondria in the forward creatine kinase reaction. It was essential to demonstrate the presence of mitochondrial creatine kinase to support the hypothesis. Using polyacrylamide gel electrophoresis and electrophoresis on cellulose acetate strips, the mitochondrial creatine kinase isozyme, as well as MM, MB, and BB isozymes, has now been demonstrated in myocardial cells in culture. Nonmuscle cells in culture also derived from neonatal rat hearts lack the mitochondrial creatine kinase isozyme. Total creatine kinase in myocardial cells is greatly decreased by treatment of the cells with adriamycin, a cardiotoxic chemotherapeutic agent, and the relative amounts of the isozymes are altered. The mitochondrial creatine kinase seems to be reduced less than either the BB or MM isozymes.

The formation of azoxy-2-phenylethane during the biological oxidation of phenylethylamine by rabbit liver microsomes

Incubation of phenylethylamine with rabbit liver microsomes, divalent manganese and a NADPH generating system leads to the formation of azoxy-2-phenylethane, among other metabolic products. Approximately 38 nmol of the azoxy compound is formed form 10 mumol of phenylethylamine during a 30 min incubation. Azoxy-2-phenylethane was identified by comparison of its chromatographic (thin-layer, high pressure liquid and gas chromatography) properties with those of an authentic standard and was confirmed by mass spectrometry. The metabolism of phenylethylamine to azoxy-2-phenylethane appears completely dependent on the presence of divalent manganese; no reaction was observed in the absence of this metal or in the presence of equivalent concentrations of cupric ions. Azoxy-2-phenylethane was mutagenic, with S-9 activation, in S. typhimurium strains TA 100 and TA 1535 but not in TA 98 or TA 1537. This report constitutes the first demonstration of the formation of an aliphatic azoxy compound from the corresponding amine by a mammalian system.

Replicative and unscheduled DNA synthesis in adriamycin-treated myocardial cells

The effect of the potent antitumor antibiotic adriamycin (ADM) on chromosome integrity, DNA replication, and unscheduled DNA synthesis was investigated in cultured rat cardiac cells. Chromosome distribution, autoradiography, and [3H]thymidine (dThd) incorporation studies were carried out on separate cultures. A 3-hr pulse of ADM at a concentration of 1 microgram/ml was sufficient to cause chromosomal aberrations that were evident for up to 3 days post-ADM treatment. At the same ADM dosage, DNA replication was depressed for up to 6 days by as much as 90%, yet the ability of the cardiac cells to repair UV-damaged DNA was not impaired. However, cells exposed to higher concentrations of ADM failed to undergo significant UV-induced repair.

Decrease of estrogen receptors induced by 17 beta-estradiol and progesterone in cultured rabbit endometrial cells

A whole cell technique to measure estradiol receptors in cultured rabbit endometrial cells is described. The estradiol receptors measured appear to be composed of at least two components: one component has high affinity but low capacity, while the other component has low affinity but high capacity. Using the assay, the effects of estradiol and progesterone pretreatment were examined on the estradiol receptor levels. It was found that both of the hormones decreased the number of estrogen receptors in the cultured cells. The finding that estradiol decreased its own receptors was unexpected and its possible relevance is discussed.