PHARMACOLOGY

 Rat diaphragm method ::

In this method increase in glycogen content of the muscle or increase in glucose uptake by muscle in response to insulin is taken as the index of potency of insulin 

Rat epididymal fat-pad method ::

Here the ability of insulin to increase CO2 production by the fat pad is taken as the parameter for the measurement of potency of the insulin preparation 

Radioimmunoassay ::

It is the estimation of the concentration of the substance in a unit quantity of preparation using radiolabelled antigens A number of drugs are estimated now a days by radioimmunoassy methods because these methods are highly specific and highly sensitive 

        The radioimmunoassay of insulin is based on the ability of human insulin (unlabelled) to displace beef s insulin (which may be labelled) from the binding sites (i.e. antibodies) The method involves the following steps :; 

1. Bovine insulin is injected into the sheep After a week the serum containing antibodies produced against bovine insulin is collected form the blood of the sheep 

2.The serum containing antibodies is exposed to radiolabelled insulin and the bound vs free ratio is determined 

3.The mixture of labelled antigen -antibodies is then added in different test-tubes labelled as standard and test About 6 concentrations of the standards are taken They are then added to different tubes and the bound vs free ratio is again determined using gamma-counter 

4.Standard curves are determined and the concentration of test insulin is determinded using this standard curve