Abstract
We have found that in normal subjects, immunoreactive insulin (IRI) response during either glucose or tolbtamide stimulus, are affected by posture, and the IRI response are greater in the sitting than in the right lateral position. We, therefore, have studied the effects of posture on insulin responses in normal subjects.
1) Gastric emptying rate of glucose, rise of blood sugar level and IRI response 30 minutes after oral glucose load were greater in the right lateral position than in the sitting position.
2) During 25 g-intravenous glucose tolerance test (iv GTT), the pretreatments with atropine (0.5 mg) or propranolol (5 mg) 10 minutes before the tests, minimalized the differences in positional changes of IRI responses. On the other hand, pretreatment with pilocarpine (7mg) or trimatoquinal (0.1 mg) enhanced those differences.
3) Pretreatment with atropine (0.5 mg) or pilocarpine (7 mg) had no significant effect on IRI responses during 25 g-iv GTT in the sitting position.
4) Vasopressin (10 units) strongly supressed IRI response during 25g-iv GTT both in the sitting and in the right lateral position, and worsend the glucose tolerance especially in the sitting position.
5) IRI disapperance curve was not affected by positional changes after intravenous injection of regular insulin (4 units).
We reported previously, that during oral GTT, the peak time of blood sugar and IRI response were more retarded in the left lateral position, and that during tolbutamide test IRI response was greater in both right and left lateral positions than in the sitting position.
Our findings, suggest the view that the gastric emptying rate, parasympathetic nerve and β2 adrenergic receptcr are the main factors responsible for the positional change in IRI response during oral GTT. On the other hand, changes in pancreatic blood flow and insulin degreading rate have little effect on the change in IRI response.
