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マウスL細胞株における温熱感受性と温熱誘導アポトーシス：加納永一¹,林　幸子¹,小久保菜穂子¹,畑下昌範¹,塩浦宏樹²,大坪俊雄³,北井隆平⁴,松本英樹¹（福井医大・¹放基,³耳,⁴脳外,²市立泉佐野病院・放）

Status of p53 in cultured murine L cells in relation to thermosensitivity, apoptosis and hsp72.: Eiichi KANO¹, Sachiko HAYASHI¹, Nahoko KOKUBO¹, Masanori HATASHITA¹, Hiroki SHIOURA², Toshio OHTSUBO³, Ryuhei KITAI⁴, Hideki MATSUMOTO¹ (¹Depts. of Exptl' Radiol., ³Otorhinolaryngol., ⁴Neurosurg., Fukui Med. Univ., ²Div. Radiol., Izumisano Hosp.)

Purpose: Status of the p53 of murine L cells was investigated in relation to the thermosensitivity, incidence of apoptosis and accumulation of p53 and hsp72.
Results: Thermosensitivities in CFU were represented by T0 values at 40, 42 and 44℃, i.e., 1080 min, 12 min or 27 min before or after the thermotolerance development and 2.5 min, respectively. Fractionated heating at 44℃ with graded interval periods at 37℃ (44℃ for 10 min - 37℃ for graded periods - 44℃ for 10 min) resulted in increase of the survival in accordance with elongation of the interval. The interval time-survival relationship was drawn that reached to subplateau followed by a full plateau of 9.5 and 25% with 37℃ intervals of 1.5 and 5 h, respectively. Marked accumulation of hsp72 was observed in 3~24 h after 44℃ heating for 10 min, which increased immediately after the heating and reached a peak 6 h after the heating. Incidence of apoptosis after the heating at 44℃ for 6.5 min (LD₅₀) increased in accordance with elongation of interval periods at 37℃ between the fractionated heatings which finally reached to a plateau of ca 25% for the interval of 6 h. The cellular content of p53 increased at 6~24 h after the heating. The exons 4 to 10 (codon 108 to 337) of p53 gene in L cells have no mutation.
Conclusion: Murine L cells of high thermosensitivity bore the wild-type p53, while hsp72 suppressed the thermosensitivity, that increased the incidence of apoptosis and therefore enhanced the thermosensitivity.