In vitro platelet ageing at 22°C is reduced compared to in vivo ageing at 3 7°C

Summary .In these studies, platelet ageing during in vitro at 22°C was compared with in vivo ageing using isotope labelling. Paired fresh and 5‐d‐stored platelets had a mean residual life‐span (MRL) of 4–8 ± 0–7d and 3–2 ± 0–9 d, respectively. After 2–1 ± 0–4 d in vivo circulation, the MRL of the fresh platelets was equivalent to that of the 5‐d‐stored in vitro platelets. This suggests that platelet ageing for 5 d in vitro at 22°C corresponds to 2–1 d in vivo ageing at 37°C. Thus, the relative ageing at 22° C C in vitro was (2.1 d/ 5d) = 0–42 of that at 37°C in vivo. A similar ageing ratio (0–44) was obtained by measurement of the decrease in MRL during storage at 22°C of platelets stored for 1, 5, 7, 10 and 14 d relative to the decrease in MRL of fresh platelets in vivo. ATP turnover rate at 22°C was compared to the rate of 37°C by measurement of the rates of platelet oxygen consumption and lactate production in vitro. In vitro ATP turnover at 22°C versus 37°C, was found to be 10–5 ± 10 versus 21–6 ± l.4/μmol/10 12 plts/min, respectively. Thus, the ATP turnover ratio (0–48) at these two temperatures suggests that the relative decrease in ageing at 22°C compared to 37°C is similar to the relative decrease in metabolic rate at this temperature.