Assessment
of the relationship between dynamic pattern of nighttime levels
of melatonin and chosen biochemical markers of bone metabolism
in a rat model of postmenopausal osteoporosis
by Zofia
Ostrowska, Beata Kos-Kudla, Elzbieta Swietochowska, Bogdan
Marek, Dariusz Kajdaniuk & Janusz GÛrski
Keywords:
melatonin, bone metabolism,
model of postmenopausal osteoporosis, female rats
Submitted:
January 21, 2001
Accepted: February 06, 2001
Abstract:
BACKGROUND:
Lately, there have been suggestions that bone mass changes
occurring in postmenopausal women may remain related to melatonin.
OBJECTIVE: To assess the relationship between the dynamic
pattern of nighttime levels of melatonin and chosen biochemical
markers of bone metabolism in ovariectomized rats – a
model of postmenopausal osteoporosis.
METHODS: Mature Wistar female rats were either ovariectomozed
or underwent a sham operation. Following this they were killed
at 02:00AM at weekly intervals for 8 weeks after surgery.
Serum levels of MEL at death related to the chosen biochemical
markers of bone formation (alkaline phosphatase - ALP; carboxyterminal
propeptide of type I procollagen - PICP, both in serum) and
resorption (cross-linked carboxyterminal telopeptide of type
I collagen - ICTP in serum; hydroxyproline - HYP and total
calcium - Ca, both excreted in urine).
RESULTS: In all ovariectomized rats changes of examined indices
of bone tissue metabolism were found to be dynamic and statistically
significant relative to the control group; however the changes
were more pronounced regarding resorption markers. Following
ovariectomy, the increase in ALP and PICP values was found
to begin at the 4th and the 1st week, while that in ICTP,
HYP and Ca at the 2nd, the1st and the 1st week, respectively.
The ALP and PICP values remained at a similar level until
the end of observation, whereas ICTP, HYP and Ca gradually
decreased. MEL levels were decreased during the 2nd week following
surgery and slightly increased 2 weeks later. The serum MEL
levels in the ovariectomized group were significantly and
negatively correlated with serum ICTP and both urinary HYP
and Ca levels.
CONCLUSION: Our findings in rats seem to corroborate the concept
of secondary changes in MEL levels co-participating in the
development of bone mass changes characteristic for postmenopausal
osteoporosis.
