[Cyclic nucleotides as intracellular transmitter substances in hormone actions]

[Experimental acceleration of fracture repair by biochemical media (author's transl)]

The influence of calcitonine, amino acids, ribonucleid acids, kallikrein, growth hormone, and cyclic adenosine 3'5' monophosphate on fracture repair was tested in rabbits. To obtain an objective measurement of callus stability the bones were bent mechanically. The force applied and the degree of bending were recorded continuously. The slope of the curve was taken as a parameter of callus stability. In the series with calcitonine no influence on fracture healing was found. Injections of ribonucleic acids, amino acids, kallidrein, and growth hormone demonstrated a limited effect on bone repair. Callus formation was stimulated by adenosine 3'5' monophosphate. Optimal results were achieved by a combination of adenosine 3'5' monophosphate, amino acids, ribonucleic acids, and kallikrein.

[The role of cyclic adenosine 3':5'-monophosphate as "second messenger" in gastric acids secretion (author's transl)]

The criteria to determine whether cyclic adenosine 3':5'-monophosphate (cyclic AMP) is or is not involved in a particular hormone response require to look for positive qualitive, quantitative and temporal correlations between the effects of the hormone on cyclic AMP levels and the physiological response. These requirements have been shown to be fulfilled in histamine and pentagastrin-stimulated gastric acid secretion of the frog (Necturus maculosus) and the rat. In dog and man, however, the available evidence does not support a role for cyclic AMP in the gastric secretory process; it remains a challenge for future research whether in those species cyclic guanosine 3':5'-monophosphate acts as an intracellular substitute for cyclic AMP.