One of the observations Dr
SubbaRow made while testing the phosphorus method
seemed to provide a clue to the mystery what happens to
blood sugar when insulin is administered. Biochemists
began investigating the problem when Frederick Banting
showed that injections of insulin, the pancreatic
hormone, keeps blood sugar under control and keeps
SubbaRow worked for 18 months on
the problem, often dieting and starving along with
animals used in experiments. But the initial
observations were finally shown to be neither
significant nor unique and the project had to be
scrapped in September 1926.
Out of the ashes of this project
however arose another project that provided the key to
the ancient mystery of muscular contraction.
Living organisms resist degeneration and
destruction with the help of muscles, and biochemists
had long believed that a hypothetical inogen provided
the energy required for the flexing of muscles at work.
Two researchers at Cambridge
University in United Kingdom confirmed that lactic acid
is formed when muscles contract and Otto Meyerhof of
Germany showed that this lactic acid is a breakdown
product of glycogen, the animal starch stored all over
the body, particularly in liver, kidneys and muscles.
When Professor Archibald Hill of the University College
of London demonstrated that conversion of glycogen to
lactic acid partly accounts for heat produced during
muscle contraction everybody assumed that glycogen was
the inogen. And, the 1922 Nobel Prize for medicine and
physiology was divided between Hill and Meyerhof.
But how is glycogen converted to
lactic acid? Embden, another German biochemist,
advanced the hypothesis that blood sugar and phosphorus
combine to form a hexose phosphoric ester which breaks
down glycogen in the muscle to lactic acid.
In the midst of the insulin
experiments, it occurred to Fiske and SubbaRow that
Embden's hypothesis would be supported if normal
persons were found to have more hexose phosphate in
their muscle and liver than diabetics. For diabetes is
the failure of the body to use sugar. There would be
little reaction between sugar and phosphorus in a
diabetic body. If Embden was right, hexose (sugar)
phosphate level in the muscle and liver of diabetic
animals should rise when insulin is injected.
Fiske and SubbaRow rendered some
animals diabetic by removing their pancreas in the
spring of 1926, but they could not record any rise in
the organic phosphorus content of muscles or livers
after insulin was administered to the animals. Sugar
phosphates were indeed produced in their animals but
they were converted so quickly by enzymes to lactic
acid that Fiske and SubbaRow could not detect them with
methods then available. This was fortunate for science
because, in their mistaken belief that Embden was
wrong, they began that summer an extensive study of
organic phosphorus compounds in the muscle "to
repudiate Meyerhof completely".
The departmental budget was so
poor that SubbaRow often waited on the back streets of
Harvard Medical School at night to capture cats he
needed for the experiments.
When he prepared the cat muscles
for estimating their phosphorus content, SubbaRow found
he could not get a constant reading in the
colorimeter. The intensity of the blue colour
went on rising for thirty minutes. Was there something
in muscle which delayed the colour reaction? If yes,
the time for full colour development should increase
with the increase in the quantity of the sample. But
the delay was not greater when the sample was 10 c.c.
instead of 5 c.c. The only other possibility was that
muscle had an organic compound which liberated
phosphorus as the reaction in the colorimeter
proceeded. This indeed was the case, it turned out. It
took a whole year.