Summary1. (-)-Isoprenaline, salbutamol, orciprenaline and quinterenol injected intravenously decreased the tension and degree of fusion of incomplete tetanic contractions of the soleus muscle of the anaesthetized cat. 2. Under the most sensitive conditions, the smallest effective dose of (-isoprenaline was of the order of 0-01 ,g/kg intravenously. Salbutamol was usually 6-10 times, orciprenaline 20-30 times and quinterenol about 35 times less potent than isoprenaline. The effects of salbutamol were about 1-6 times, of orciprenaline about 1-8 times and of quinterenol more than 20 times as long lasting as those of (-)-isoprenaline.3. The effects of the sympathomimetic amines were blocked by propranolol, H56/28, H35/25 and butoxamine but not by ICI 50172. The combined results with agonists and antagonists indicate that the receptors involved can be classified as of the P2 type. 4. The effect of the amines on the cat soleus muscle appears to be analogous to that causing enhancement of physiological tremor in man, which suggests that skeletal muscle tremor may be an occasional unwanted side effect of the use of these bronchodilators.

Glycosylated total protein (GTP) and glycosylated albumin (GALb) were measured in serum using aminophenylboronic acid affinity chromatography and the results were compared with those found using the fructosamine assay. The percentage GTP and GALb found by affinity chromatography correlated well with fructosamine values in the sera of a group of non-diabetic and diabetic patients (fructosamine vs GTP, r = 0.91, p less than 0.001; fructosamine vs GALb, r = 0.91, p less than 0.001). Results of each method gave similar correlations when compared with the degree of diabetic control assessed by glycosylated haemoglobin (GHb) and fasting plasma glucose (FPG) (fructosamine vs FPG, r = 0.74, p less than 0.001; GTP vs FPG, r = 0.75, p less than 0.001; GALb vs FPG, r = 0.79, p less than 0.001; fructosamine vs GHb, r = 0.79, p less than 0.001; GTP vs GHb, r = 0.81, p less than 0.001; GALb vs GHb, r = 0.84, p less than 0.001). Both methods could equally discriminate between groups of non-diabetics and diabetic patients (p less than 0.001) and showed similar temporal changes after starting insulin therapy.

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S U M M A R YI . The actions and interactions of compounds with phosphodiesterase-inhibiting activity and of sympathomimetic amines have been studied on contractions of skeletal muscles in chloralose-anaesthetized cats treated with bethanidine and in which the adrenals were excluded from the circulation.2. Compounds with phosphodiesterase-inhibiting activity, ICI 63,197, ICI 58,301, papaverine, theophylline, and dipyridamole, potentiated isoprenaline in its depressant effect on tension and fusion of incomplete tetanic contractions of the slow-contracting soleus muscle, the order of potency being as listed. ICI 63,197 and theophylline also potentiated adrenaline and salbutamol in depressing contractions.3. ICI 63,197 potentiated isoprenaline in its enhancing effect on tension and degree of fusion of incomplete tetanic contractions of the fast-contracting tibialis anterior and flexor digitorum longus muscles.4. The results are compatible with the hypothesis that the effects of sympathomimetic amines on muscle contractility are mediated by cyclic adenosine-3',5'-monophosphate, although this nucleotide and its dibutyryl analogue, injected intra-arterially, were themselves without any consistent effect.5. High doses of ICI 63,197, ICI 58,301, papaverine and dipyridamole, themselves produced isoprenaline-like effects on the soleus muscle. These effects were partially antagonized by ( f )-propranolol, ( +)-propranolol, or sotalol. The (+)-isomer of propranolol was only about ten times less potent than racemic propranolol in this respect. This antagonistic action of propranolol and sotalol appeared to be independent of b-adrenoceptor blockade.

Summary The effects of (–)‐isoprenaline and the new β‐adrenoceptor agonist, MJ‐9184–1, on the lungs, on the cardiovascular system, and on slow contracting skeletal muscle have been compared in cats under chloralose anaesthesia. Both amines reduced the increases in airways resistance produced by 5‐HT, depressed incomplete tetanic contractions of the soleus muscle, lowered the blood pressure and produced an increase in heart rate. In comparison with (‐)‐isoprenaline, MJ‐9184–1 had a long duration of action. The effects of MJ‐9184–1 and (–)‐isoprenaline were antagonized by the β‐adrenoceptor antagonist, propranolol. MJ‐9184–1 was approximately half as potent as (–)‐isoprenaline in its effects on pulmonary resistance and soleus muscle contractility, and one seventh as potent in producing chronotropic effects in the heart. These results suggest that MJ‐9184–1 possesses some specificity as a β2 receptor stimulant.