“…The effects of the guanylnucleotides and their interactions with PTH resemble those seen with chick kidney (Michelangeli et al 1977) and with other hormones and target tissues (see Rodbell, Lin, Salomon, Londos, Harwood, Martin, Rendell & Berman, 1974, for review). In particular, the relatively small effect of GTP on adenylate cyclase and its failure to enhance hormone responsiveness was noted in chick kidney membranes , in rat fat cell membranes (Harwood, Low & Rodbell, 1973) and in dog myocardium (Lefkowitz, 1974).…”