lOp
Medical Research Society
may contribute to the vascular complications of the disease.
Several other organs are rich sources of prostacyclin, particularly the myometrium of the rat uterus. In this tissue
prostacyclin production increases during gestation, reaching a
maximum at parturition, and may play a role in regulating
uterine function. Diabetic women develop complications of
pregnancy; we have studied the influence of experimental
diabetes on prostacyclin generation by myometrial and vascular
tissue from pregnant rats.
Diabetes was induced in female Wistar rats by streptozotocin
(80 mg/kg i.v.) and control rats were injected with vehicle only.
One group of animals was made diabetic and mated after five
weeks (chronically diabetic). Another group was rendered
diabetic on day 17 of pregnancy (acutely diabetic). Animals
were killed on days 2()"'22 of pregnancy and appropriate tissues
were removed, chopped and incubated for 15 min at 20°e. The
prostacyclin contents of the media were determined by inhibition
of ADP-induced aggregation of rabbit citrated platelet-rich
plasma against authentic prostacyclin (gift of Wellcome
Laboratories).
In acutely diabetic animals killed on day 22 of pregnancy,
prostacyclin release from the myometrium was 3·9 ± SEM 0·31
ng/mg (n = 8) vs 4·52 ± 0·3 ng/mg in controls, (N.S.). In aortic
tissue prostacyclin synthesis was reduced from 5·75 ± 1·23
ng/mg (controls) to 3·45 ± 1·12 ng/mg (diabetics). a 38%
reduction (N .S.). In chronically diabetic rats killed on day 20 of
pregnancy myometrial prostacyclin generation was 2·56 ± 0·36
ng/mg vs 2·94 ± 0·24 in controls (N.S.; n = 9). However, in
aortic tissue, control production was 2·5 ± 0·39 ng/mg and this
was reduced in the diabetics to 0·85 ± O· 17 ng/rng, a 66%
decrease (P < 0·001).
The experiments show that whereas myometrial prostacyclin
synthesis is unaffected by diabetes, production by aortic tissue is
markedly depressed, indicating a degree of selectivity. Furthermore. the reduction in vascular prostacyclin production appeared to be related to the duration of diabetes. Other tissues are
presently being studied.
32. SERUM LONG ACTING THYROID STIMULATOR
(LATS) AND LATS-PROTECTOR (LATS-P) IN GRAVES'
DISEASE
COMPLICATED
BY
LOCALIZED
MYXOEDEMA
e. A. HARDISTY AND D. S. MUNRO
Department oj Medicine, Clinical Sciences Centre, Northern
General Hospital, Sheffield S5 7AU, U.K.
When localized myxoedema occurs in Graves' disease there is
often very high serum LATS activity. However. this association
is not invariable and no pathogenetic role for this IgGassociated activity is known (Schermer. Roenigk, Schumacher
& McKenzie. 1970. Archives oj Dermatology. 102, 62-67).
Serum LATS-P, a closely related IgG activity which is present
in the majority of cases of untreated Graves' disease. usually
coexists in LA TS-positive sera in a substantially greater
concentration. Its association with localized myxoedema has not
been studied and serial studies have not been performed for
either activity.
Thirteen patients (12 female. one male) with localized
myxoedema and a history of Graves' disease were examined. In
12. serum LATS was detectable with a wide range of activity
from 2 -4 to 1000 units/ml. Serum LA TS- P was detected in all.
including the LA TS-negative patient. with a range of activity
from 46 to 8390 units/ml. Serial studies for at least 2 years were
conducted in eight patients. In three there was no change in
either skin lesions or in serum LATS and LATS-P. In four. the
lesions disappeared; whereas in three this was associated with
marked decline in both activities. in one no significant change
occurred. One patient improved clinically as both LA TS and
LA TS P declined.
This study has demonstrated the high prevalence of LATS
and LATS-P in localized myxoedema. In the sole LATSnegative patient, there was a high concentration of LATS- P. The
role of these activities in the pathogenesis of the disease remains
unknown but in serial studies falls in activity were usually
associated with clinical improvement.
33. SIMILARITY OF HUMAN THYROID ADENYLATE
CYCLASE RESPONSE TO THYROTROPHIN (TSH) AND
THYROID STIMULATING IMMUNOGLOBULINS (TSlg)
e. A. OLLIS, S. MAcNEIL, A. CRAWFORD, L. CHIVERS, H.
HUMPHRIES. D. S. MUNRO AND S. TOMLINSON
Department oj Human Metabolism and Clinical Biochemistry,
University ojSheffield Medical School, Sheffield 10, U.K.
TSlg produced in Graves' disease appear to have similar effects
to TSH on the thyroid. but there have been few reports of a
stimulatory effect of TSlg on thyroid membrane adenylate
cyclase activity. Moreover, a lag in the activation of thyroid
adenylate cyclase by TSlg, which is not apparent with TSH, has
been observed. suggesting that TSH and TSlg may act
differently. Human thyroid membranes which respond to TSH
but not to TSlg show an increased response to TSH and a
significant response to TSlg in the presence of a crude cytosol
preparation (Ollis, Tomlinson, MacNeil, Crawford & Munro,
1979, FEBS Letters. 107, 269-272). In the present study we
compared the activation of thyroid adenylate cyclase by TSH
and TSlg.
Membranes were prepared from non-toxic goitres. and
cytosol from human platelets or rat osteogenic sarcoma cells.
(The adenylate cyclase-enhancing factor in cytosol is neither
species- nor tissue-specific; MacNeil, Crawford, Amirrasooli,
Johnson, Pollock, Ollis & Tomlinson, 1980, Biochemical
Journal. 188, 393--400.) TSlg were prepared by ammonium
sulphate precipitation of serum from patients with Graves'
disease. In the absence of cytosol no response to TSlg was
detectable. In the presence of cytosol the optimum activation of
the enzyme by TSH and by TSlg showed a similar pH (pH 7·8).
substrate requirement (I mmol/I ATP, 5 mmol/l Mg 2+) and
cyclic AMP production was linear over a similar range of
protein concentrations. Under these conditions the response to a
maximally stimulating concentration of TSH (250 m-units/ml)
was linear for 20 min and there was no obvious lag in the
response to TSlg. which continued for up to 30--40 min at
37°C.
We conclude that TSH and TSlg do in fact activate the
thyroid adenylate cyclase in a similar manner.
34. ESTIMATES OF CALCITONIN SECRETION RATES
IN HEALTH. PAGET'S DISEASE AND RENAL FAILURE
J. A. KANIS,G. HEYNEN. T. CUNDY ANDS. GASPAR
Department oj Human Metabolism and Clinical Biochemistry,
University oj Sheffield Medical School, Sheffield S 10 2RX,
UK
The endogenous secretion rate of calcitonin (CT) in man is
unknown. and hence it is not clear which. if any. of the actions
of calcitonin given exogenously can be considered physiological. We have measured plasma concentrations of immunoreactive CT (iCT) during the continuous infusion of human CT
(20--40 ,ug/h for 24 h). From the concentrations of iCT
obtained, the calculated metabolic clearance rates varied little.
and were similar in four patients with Paget's disease (mean
930 ± SEM 76 litres/day) and in four normal subjects
(851 ± 131 litres/day), despite large differences in basal levels of
plasma iCT (range 50-227 pg/ml). This suggests that variations in plasma concentrations of iCT between patients are
mainly due to variations in endogenous secretion rates.
Calculated secretion rates (120 ± 22 ,ug/day) in normal persons
were similar to those in 10 patients with Paget's disease
calculated from the half-life of exogenously given human
calcitonin (halftime 10·6 ± 1·2 min).
Patients with renal failure have higher plasma concentrations