Summary
Release of previously incorporated45Ca from fetal rat long bones was determined with the diterpene forskolin, both in the absence and presence of parathyroid hormone (PTH) and calcitonin (CT). In the absence of hormone, increased bone resorption was observed with 10−7M forskolin, but biphasic responses, consisting of initial decreases in45Ca release that were followed by increased calcium mobilization, were produced with 10−6M and 10−5M forskolin. Inhibition of45Ca release was pronounced and delayed more with 10−5M forskolin while the greatest stimulation of bone resorption was elicited by 10−6M forskolin, a response that was inhibited by 100 mU/ml CT. In the presence of 250 ng/ml PTH, a synergistic enhancement of45Ca release occurred with 10−7M forskolin treatment while, in contrast, calcium mobilization was inhibited by 10−6M and 10−5M forskolin. Inhibition by 10−6M forskolin was characterized by “escape” while that of 10−5M forskolin was continuous over a 5 day interval. Inhibition throughout the experimental period also was noted when 10−5M forskolin was combined with 2.5 ng/ml PTH, but no effect on calcium mobilization was observed upon addition of 10−7M forskolin and, rather than inhibition, an enhancement of45Ca release occurred when 10−6M forskolin was combined with 2.5 ng/ml PTH. Inhibition of 250 ng/ml PTH, but lack of inhibition of 2.5 ng/ml PTH by 10−6M forskolin suggests a 10−6M forskolin-sensitive portion of PTH-mediated calcium efflux. Absence of “escape” when 10−5M forskolin is combined with 250 ng/ml PTH suggests that heterologous desensitization may not play a major role in the “escape” which occurs with 10−6M forskolin.
Similar content being viewed by others
References
Seamon KB, Daly JW (1981) Forskolin: a unique diterpene activator of cyclic AMP-generating systems. J Cyclic Nucleotide Res 7:201–224
Martz A, Thomas ML (1983) Effects of forskolin on bone: stimulation of cyclic AMP accumulation and calcium efflux from chick embryo tibiae in organ culture. Biochem Pharmacol 32:3429–3433
Lerner U, Fredholm BB, Ransjo M (1984) Transient inhibition of calcium mobilization from cultured mouse calvarial bones by the adenylate cyclase stimulator forskolin. Acta Physiol Scand 120:159–160
Henry HL (1985) Parathyroid hormone modulation of 25-hydroxyvitamin D3 metabolism by cultured chick kidney cells is mimicked and enhanced by forskolin. Endocrinology 116:503–510
Seamon K, Daly JW (1981) Activation of adenylate cyclase by the diterpene forskolin does not require the guanine nucleotide regulatory protein. J Biol Chem, 256:9799–9801
Clark RB, Goka TJ, Green DA, Barber R, Butcher RW (1982) Differences in the forskolin activation of adenylate cyclases in wild-type and variant lymphoma cells. Mol Pharmacol 22:609–612
Darfler FJ, Mahan LC, Koachman AM, Insel PA (1982) Stimulation by forskolin of intact S49 lymphoma cells involves the nucleotide regulatory protein of adenylate cyclase. J Biol Chem 257:11901–11905
Luben RA, Wong GL, Cohn DV (1976) Biochemical characterization with parathormone and calcitonin of isolated bone cells: provisional identification of osteoclasts and osteoblasts. Endocrinology 99:526–534
Peck WA, Burks JK, Wilkins J, Rodan SB, Rodan GA (1977) Evidence for preferential effects of parathyroid hormone, calcitonin and adenosine on bone and periosteum. Endocrinology 100:1357–1364
Rodan GA, Martin TJ (1981) Role of osteoblasts in hormonal control of bone resorption-A hypothesis. Calcif Tissue Int 33:349–351
Chambers TM, Dunn CJ (1982) Osteoclast activity is determined by intraoellular cAMP levels. In: Silberman M, Slavkin HC (eds) Current advances in skeletogenesis. Congress Series 589, Excerpta Medica, Amsterdam, p 154
Lerner U, Gustafson GT (1981) Delayed stimulatory effect of cyclic AMP on bone resorption in vitro. Acta Endocrinol 97:281–288
Conaway HH, Diez LF, Raisz LG (1986) Effects of prostacyclin and prostaglandin E1 (PGE1) on bone resorption in the presence and absence of parathyroid hormone. Calcif Tissue Int 38:130–134
McLeod JF, Raisz LG (1981) Comparison of inhibition of bone resorption and escape with calcitonin and dibutyryl 3′5′ cyclic adenosine monophosphate. Endocr Res Commun 8:49–59
Stern PH, Raisz LG (1979) Organ culture in bone. In: Simmons DJ, Kunin AS (eds) Skeletal research: an experimental approach. Academic Press, New York, p 21
Steel RCD, Torrie JH (1960) Principles and procedures of statistics. McGraw-Hill, New York, pp 66, 106, 107, 111, 132
Livesey SA, Kemp BE, Re CA, Partridge NC, Martin TJ (1982) Selective hormonal activation of cyclic AMP-dependent protein kinase isoenzymes in normal and malignant osteoblasts. J Biol Chem 257:14983–14987
Livesey SA, Collier G, Zajac JD, Kemp BE, Martin TJ (1984) Characteristics of selective activation of cyclic AMP-dependent protein kinase isoenzymes by calcitonin and prostaglandin E2 in human breast cancer cells. Biochem J 224:361–370
Litvin Y, PasMantier R, Fleisher N, Erlichman J (1984) Hormonal activation of the cAMP-dependent protein kinases in AtT20 Cells. J Biol Chem 259:10296–10302
Friedman J, Au WYW, Raisz LG (1968) Responses of fetal rat bone to thyrocalcitonin in tissue culture. Endocrinology 82:149–156
Werner JA, Gordon SJ, Raisz LG (1972) Escape from inhibition of resorption in cultures of fetal bone treated with calcitonin and parathyroid hormone. Endocrinology 90:752–759
Tashjian AH Jr, Wright DR, Ivey JL, Pont A (1978) Calcitonin binding sites in bone: relationship to biological response and “escape”. Rec Prog Hor Res 34:285–334
Mokhtari A, Dokhac L, Tanfin Z, Harbon S (1985) Forskolin modulates cyclic AMP generation in the rat myometrium: interactions with isoproterenol and prostaglandins E2 and I2. J Cyclic Nucleotide Prot Phosphor Res 10:213–228
Sibley DR, Lefkowitz RJ (1985) Molecular mechanisms of receptor desensitizating using the β-adrenergic receptor-coupled adenylate cyclase system as a model. Nature 317:124–130
Benovic JL, Pikes LJ, Cerione RA, Staniszewski C, Yoshimasa T, Codina J, Caron MG, Lefkowitz RJ (1985) Phosphorylation of the mammalian β-adrenergic receptor by cyclic AMP-dependent protein kinase. J Biol Chem 260:7094–7101
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Conaway, H.H., Abraham, R.L. & Wadkins, C.L. Effects of forskolin on bone resorption in the absence and presence of parathyroid hormone and calcitonin. Calcif Tissue Int 40, 276–281 (1987). https://doi.org/10.1007/BF02555261
Received:
Revised:
Issue Date:
DOI: https://doi.org/10.1007/BF02555261