PHARMACOLOGY

 BIOASSAY OF POSTERIOR PITUITARY INJECTION ::

Principle ::

Potency of the test and the std sample is compared with reference to their respective oxytocic pressor and anti -diuretic activity by a biological method 

Standard preparation and unit ::

1unit = 0.5 mg 

It is the quantity of dried acetone - extracted substance obtained from the posterior lobes of fresh pituitary glands of oxen This unit is specified by the Ministry of Health of the Govt of India and is the same as the International Unit 

Preparation ::

Pituitary glands of oxen are obtained from the slaughter house They are made free from other tissues and extracted repeatedly with acetone to remove the attached tissues The gland is cut into small pieces and again extracted with acetone Then it is dried over CaCI2 in an evacuated desiccator (for five hours ) It is powdered and again dried over phosphorous pentoxide Then it is stored in sealed ampoules 

    Exactly 20 units of the powder is weighed and extracted with dilute solution of glacial acetic acid it is diluted to represent finally 2 units /ml and is stored at 0. C

Oxytocic activity ::

As soon as the female guinea pigs wean they should be separated from the males and used for the test when they weigh between 170-350 g The animal is isolated and one horn is suspended in a bath containing as following ::

Dale s Solution ::

Sodium Chloride                                                                                 9.0 g.

Potassium Chloride                                                                             0.42 g. 

Calcium Chloride                                                                                0.24 g.

Sodium Bicarbonate                                                                            0.50 g.

Glucose                                                                                                0.50 g.

Magnesium Chloride                                                                            0.25 g.

Distilled Water add upto                                                                       1000 ml 

    The bath is maintained at a temperature of 37.C and is oxygenated The contractions of the uterine horn are recorded by a frontal lever on the surface of a smoked paper fixed on a slowly revolving drum 

    Standard pituitary extract in a dose of 0.05-0.1 unit is added into the inner bath This causes the uterus to contract and when contraction is complete the solution of the bath is drained out and fresh solution is run in and the muscle is allowed to relax Repeated additions of pituitary extract may be made at regular intervals The potency of the test sample is calculated by comparing the height of contraction with that produced by the std sample