Secretion of albumin and induction of CYP1A2 and CYP3A4 in novel three-dimensional culture system for human hepatocytes using micro-space plate.

We evaluated a novel primary three-dimensional culture system for human hepatocytes using micro-space plates. The functional activity of human hepatocytes in primary culture was determined by measuring albumin secretion from hepatocytes to medium and measuring expression levels of albumin, CYP1A2 and CYP3A4 mRNA. Albumin secretion was higher in micro-space plates compared with traditional plates after 72 h of culture; the levels of albumin secretion from hepatocytes to medium in culture using micro-space plates after 96 h of culture were 2.7-fold higher than those in culture using traditional plates, and secretion of albumin in micro-space plate culture subsequently remained constant. Expression levels of albumin, CYP1A2 and CYP3A4 mRNA in the culture of hepatocytes were significantly higher using micro-space plates than using traditional plates. The inducibility of CYP1A2 and CYP3A4 mRNA after exposure to inducers in hepatocyte culture on micro-space plates was comparable to that in culture on traditional plates, while expression of CYP1A2 and CYP3A4 mRNA after exposure to inducers was higher on micro-space plates than on traditional plates. The present study demonstrates that a novel primary three-dimensional culture system of cryopreserved human hepatocytes using micro-space plates could be used for evaluating the induction of drug-metabolizing enzymes in humans. This in vitro method may thus be useful for screening the induction potency of new drug candidates.

Circadian changes in core body temperature, metabolic rate and locomotor activity in rats on a high-protein, carbohydrate-free diet.

Ingestion of a high-protein meal results in body weight loss due to elevated energy expenditure, while also increasing satiety and decreasing subsequent food intake. The present study aimed to clarify the effects of a high-protein, carbohydrate-free diet (HPCFD) on these physiological indicators from a circadian perspective. Rats were given HPCFD or a pair-fed normal protein content diet (20% protein; NPD) for 4 d. The HPCFD group lost more body weight than the NPD group. Oxygen consumption (VO(2)) in the HPCFD group did not change during the experimental period, and tended to be higher during the light (L) phase than in the NPD group. Carbon dioxide production (VCO(2)) during the L phase was higher in the HPCFD group than in the NPD group, where VCO(2) was gradually decreased during the last dark (D) phase and throughout the L phase. The HPCFD group exhibited higher daily core body temperature (T(b)), particularly during the late D phase and throughout the L phase when compared to the NPD group. Locomotor activities during the D phase of the NPD group tended to gradually increase and were thus significantly higher than in the HPCFD group. These results suggest that HPCFD, even if energy intake is insufficient, maintains circadian changes in metabolic rates, resulting in maintenance of elevated daily T(b) and body weight reduction without increasing activity.