RESUMO
KCP-4 is a cisplatin-resistant cell line established from human epidermoid carcinoma KB-3-1 cells. Although our previous study revealed that one of the mechanisms for cisplatin resistance in KCP-4 cells is the activation of NF-κB, its high resistance is considered to be induced by multiple mechanisms. In the present study, we explored other factors involved in the development of cisplatin resistance in KCP-4 cells. Since it has been reported that an unknown efflux pump exports cisplatin from KCP-4 cells in an ATP-dependent manner, we examined 48 types of ATP-binding cassette proteins as candidate cisplatin efflux transporters. The mRNA expression levels of ABCA1, ABCA3, ABCA7 and ABCB10 in KCP-4 cells were higher when compared to those in KB-3-1 cells. These expression levels in cisplatin-sensitive revertant KCP-4 cells (KCP-4R cells), were reduced in parallel with the sensitivity of these cells to cisplatin and their intracellular accumulation of cisplatin. Next, we investigated the occurrence of mutations in p53 in KCP-4 cells. We found a heterozygous missense mutation at codon 72 (p.Pro72Arg) in p53 of both KCP-4 and KB-3-1 cells, but the protein expression level of p53 in KCP-4 cells was higher when compared to that in KB-3-1. These results suggest that ABCA1, ABCA3, ABCA7 and ABCB10 are candidate genes for the cisplatin efflux transporter that is involved in the cisplatin resistance of KCP-4 cells, and that the mutation at codon 72 of p53 may contribute to the development of cisplatin resistance.
Assuntos
Carcinoma de Células Escamosas/tratamento farmacológico , Cisplatino/farmacologia , Resistencia a Medicamentos Antineoplásicos/genética , Proteínas Associadas à Resistência a Múltiplos Medicamentos/genética , Proteína Supressora de Tumor p53/genética , Transportador 1 de Cassete de Ligação de ATP/genética , Transportadores de Cassetes de Ligação de ATP/genética , Antineoplásicos/farmacologia , Sequência de Bases , Carcinoma de Células Escamosas/genética , Linhagem Celular Tumoral , Ativação Enzimática , Humanos , NF-kappa B/metabolismo , RNA Mensageiro/biossíntese , Análise de Sequência de DNARESUMO
Milk is an effective post-exercise rehydration drink that maintains the net positive fluid balance. However, it is unclear which components are responsible for this effect. We assessed the effect of milk protein solution (MPS) obtained by dialysis on body fluid retention. Milk, MPS, milk electrolyte solution (MES), sports drink and water were administered to male Wistar rats at a dose of 6 ml/rat after treadmill exercise. Total body fluid retention was assessed by urine volume 4 h after administration of hydrating liquids. The rate of gastric emptying was evaluated by a tracer method using (13)C-labelled acetate. Plasma osmolality, Na and K levels, and urinary Na and K were measured by HPLC and osmometry, respectively. The gastric emptying rate was not delayed by MPS. During 4 h of rehydration, cumulative urine volumes differed significantly between treatment groups (P < 0·05) with 4·9, 2·2 and 3·4 ml from water-, milk- and MPS-fed rats, respectively. Thus, MPS elicited 50 % of the total body fluid retention of milk. Plasma aldosterone levels were significantly higher in MPS- and milk-fed rats compared with water-fed rats. Plasma osmolality was maintained at higher levels in MPS-fed rats than in water- and MES-fed rats (P < 0·05). Cumulative urine Na excretion was also suppressed in the milk- and MPS-fed groups compared with the MES-fed group. Our results demonstrate that MPS obtained by dialysis clearly affects net body water balance without affecting gastric emptying after exercise. This effect was attributed to retention of Na and water, and maintenance of plasma osmolality.
