Cyclic amp and serum arrest of the mitotic activity of human diploid fibroblasts |
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Authors: | R T Dell'Orco T J Martin W H J Douglas |
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Institution: | (1) Biomedical Division, The Samuel Roberts Noble Foundation, Inc., 73401 Ardmore, Oklahoma;(2) The W. Alton Jones Cell Science Center, 12946, New York, Lake Placid |
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Abstract: | Summary Mitotic activity in confluent cultures of human diploid fibroblasts was arrested by the reduction of the serum concentration
of the incubation medium to 0.5% or by the addition of 0.5mm 6-N, 2′-O-dibutyryl-adenosine 3′:5′-cyclic monophosphate (db cAMP). Under either of these conditions, cultures maintained
a constant cell number for 14 days; cultures continuously exposed to medium containing 10% serum doubled their cell number
during this 14-day period. The protein content per cell decreased by 20% when cells were maintained with 0.5% serum whereas
that of cells exposed to db cAMP remained constant. Ultrastructural studies revealed that cells exposed to db cAMP exhibited
a morphology typical of cells cultured with 10% serum alone, whereas cells incubated with 0.5% serum showed the ultrastructural
changes in mitochondria, endoplasmic reticulum and Golgi complex previously identified with low-serum arrest. Cellular adenosine
3′:5′-cyclic monophosphate (cAMP) levels remained constant during the 7-day growth period in which confluency was attained,
as well as during the 14-day arrested period with 0.5% serum. These results indicated that the mitotic inhibition induced
by reducing the serum concentration of the incubation medium was not mediated by increased intracellular levels of cAMP and
differed from that induced by the addition of exogenous db cAMP. |
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Keywords: | cAMP low serum mitotic arrest |
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