Adenosine 5'triphosphate transport and accumulation during the cold preservation of rat hepatocytes in University of Wisconsin solution

AIM: We used isolated hepatocytes to investigate how different concentrations of ATP in the University of Wisconsin (UW) solution affected both cellular ATP content and cell viability during the cold storage and the rewarming step. The mechanism involved in ATP transport and accumulation in hypothermia was also determined. METHODS: The cells were preserved up to 72 h in different conditions: UW solution without ATP (a-group), UW+5 mmol/L ATP (b-group), and UW+10 mmol/L ATP (c-group). The ATP content and the cell viability (LDH release) were determined during the cold storage and the rewarming step. In the groups a and c, the respiratory function of the cells at rewarming was studied. In addition, the cell volume of hepatocytes and the mechanism involved in ATP transport and accumulation were assessed. The extracellular degradation of exogenous nucleotides during transport experiments was investigated by a HPLC technique. RESULTS: After three days of cold storage a loss of cellular ATP content was observed in hepatocytes preserved either without nucleotides (a-group) or with 5 mmol/L ATP (b-group). In contrast, 10 mmol/L ATP (c-group) was able to maintain a normal ATP cellular content, with only a 6% diminution after 72 h of cold storage. The respiratory function was significantly different in hepatocytes preserved with 10 mmol/L ATP than without ATP. No significant change was detected For the three groups in cellular volume during the cold storage. We also report that the time course accumulation of [3H]-ATP by cold stored hepatocytes is a rapid process that is completed after 180 s with linear dependence on the extracellular ATP concentration (linear fitting results in a slope of 0.5624±0.1179 mmol/L ATP intracell/mmcl/L ATP extracell). CONCLUSION: Our results show that, during hypothermic storage in UW solution, hepatocytes are permeable to ATP by a diffusive mechanism. Also, we found that it is ATP the main extracellular nucleotide available for transport and it is not the breakdown products.

INHIBITORY EFFECTS OF ADENOSINE 5' -TRIPHOSPHATE ON COCHLEAR FUNCTION OF GUINEA PIG

Objective To study effects of adenosine 5’-triphosphate (ATP) on cochlear function of guineapig. Methods After perfusion of ATP into perilymphatic spaces of the guinea pig cochlea, summating potential(SP) , cochlear microphonic ( CM) , auditory nerve compound action potential ( CAP) , distortion product otoa-coustic emission (DPOAE) and auditory brainstem response (ABR) were measured. Results The resultsshowed concentration-dependent effect of ATP on the response alterations of bioelectric activity in cochlea. Adminis-tration of Immol/L ATP caused an increase both in the amplitude of the SP and in the threshold of ABR, a decreasein amplitude of the CAP and DPOAE. In addition, response alterations of the CAP and DPOAE showed in an inten-sity- and frequency-dependent manner, respectively. At levels of 20 - 70dB nHL sound intensity, lmmol/L ATPcaused a significant decrease in the CAP amplitude, while at moderate and high frequency ranges of 2 -8kHz it re-duced DPOAE amplitude significantly. 330μmol/L ATP also increased the threshold of ABR. Conclusion ATPthrough perilymphatic perfusion could inhibit cochlear function of guinea pig.

Changes in the Contents of ATP and Its Related Breakdown Compounds in Various Tissues of Oyster During Frozen Storage

The changes in the contents of adenosine 5’-triphosphate (ATP) and its related breakdown compounds were investigated in the adductor muscle, mantle, gill and body trunk of oyster (Crassostrea gigas) during frozen storage at -20℃ and -30℃ and compared with that of the fresh oyster. The investigation was performed using an HPLC system. Different extents of ATP decomposi- tion were found in various tissues frozen at the two temperatures. The K, K’ and A.E.C values were calculated as the chemical fresh- ness indices. Considering the results of sensory evaluation, the A.E.C. value in body trunk at -20℃ and -30℃ could be used as the best freshness index for frozen oyster.