CASE FILES: BIOCHEMISTRY
[18.2] Rapidly elevating body temperature was observed in this patient. The
underlying cause for this pyretic episode is which of the following?
A. Hypothalamic upward adjustment of body temperature set point in
response to cold operating room temperature
B. Muscles producing heat from exertion of contraction
C. Uncoupling proteins allowing dissipation of the mitochondrial
hydrogen ion gradient releasing energy as heat
D. Metabolism of fatty acids from lipid storage depots releasing heat
E. Elevated consumption of ATP to support muscle contraction releas-
[18.3] Which of the following best describes the mechanism of action of
dantrolene in the treatment of MH?
A. Decrease of Ca2+ release
B. Reduction of body temperature with hypothalamic set temperature
C. Effect on mitochondrial ATP production
D. Nuclear transcription attenuation
E. Recoupling of the sodium and ATP channels
A nsw ers
C. Release of Ca2+ triggers actin-myosin reaction, prompting muscle
contraction. Neither fear of surgery nor hydrogen ion levels causes
concerted muscle contraction. Increased pyruvate/lactate or tempera-
ture tends to counteract contraction.
C. Malignant hyperthermia does not involve central brain control of
temperature but is caused by metabolic alterations. Regardless of the
source of energy—whether fatty acids or the utilization of ATP to
support muscle contraction—the electron transport chain is involved.
Uncoupling of oxidation from ADP phosphorylation is caused by
uncoupling proteins that dissipate energy as heat. This causes the ele-
vation of body temperature seen in this patient.
A. Dantrolene brings about reduction in contraction of skeletal muscles
by decreasing the amount of Ca2+ released from the sarcoplasmic retic-
ulum. In addition, supportive care is aimed at decreasing body temper-
ature and correcting the metabolic acidosis and electrolyte balance.