PLASMA TESTOSTERONE LEVELS IN INTACT AND
HEMICASTRATED GROWING COCKERELS F. J. M. DRIOT, M. DE REVIERS AND J. WILLIAMS I.N.R.A., Station de Recherches Avicoles, 37380 Nouzilly, France
(Received 21 April 1978) SUMMARY
Changes in the levels of testosterone in plasma were measured by radioimmunoassay in blood samples taken at frequent intervals between 2 and 26 weeks of age from entire
cockerels and cockerels hemicastrated before 2 weeks of age. In both groups the pattern of testosterone secretion could be divided into three clearly defined phases. In young birds, the levels of testosterone in plasma were low (0\m=.\3ng/ml) but in the prepubertal period, at 11 weeks of age, they started to rise and continued to rise until 22 weeks of age when adult levels, which fluctuated between 2\m=.\5and 3\m=.\5ng/ml, were reached. In the immediate period after hemicastration, the concentration of testosterone decreased temporarily. From 11 weeks of age the levels of testosterone in the hemicastrated birds were approximately 75% of those in intact birds. These results are discussed in relation to the compensatory testicular hypertrophy which occurs in growing cockerels hemicastrated at an early age. INTRODUCTION
In various species, hemicastration of the young animal induces compensatory testicular hypertrophy. This has been demonstrated in the rat (Jacobsohn & Norgren, 1965; Figarova, 1969; Liang & Liang, 1970; Hochereau de Reviers, 1975; Ojeda & Ramirez, 1972; Ramirez & Sawyer, 1974), ram (Voglmayr & Mattner, 1968; Hochereau de Reviers, 1975; Alti & Rüttle, 1976), stallion (Frerichs, 1977), field vole (Martinet & Meunier, 1975), cockerel (Benoit, 1925; Domm & Juhn, 1927), duck (Benoit, 1930) and white-crowned sparrow (Farner, Morton & Folle«, 1968). It was of interest, therefore, to compare the levels of testosterone in the plasma of intact and hemicastrated cockerels to establish the steroidogenic capability of the remaining testis in hemicastrated cockerels. MATERIALS AND METHODS
Ninety-five male birds of an egg-type strain (M 55) were purchased commercially from Station Experimentale Avicole du Magneraud (I.N.R.A., 17700 Surgeres, France), raised on the floor from the age of 1 week until 16 weeks of age and then caged singly. The light : darkness schedule was 16 h light : 8 h darkness throughout the experiment. The ambient temperature was gradually decreased from 35 to 20 °C during the first 6 weeks and then kept constant at this value. The cockerels were watered and fed ad libitum on a diet consisting of 17% protein until week 6 and 14% protein thereafter (11-7 MJ/kg). Experimental approach An examination of the changes in concentration of testosterone in plasma after hemi¬ castration of the prepubertal cockerel was carried out in two stages. The first involved
examination of the changes occurring immediately after the operation and the second entailed a long-term examination of the levels of testosterone in the plasma until sexual maturity. In both cases, hemicastration and sham-operations were performed under ether anaesthesia when the animals were 9-13 days old. In the first part of the study, all animals were starved for 24 h before the operation. Blood sampling was performed by frontal cardiac puncture up to 5 weeks of age from 15 hemicastrated, 15 sham-operated and 15 intact cockerels, and thereafter by venepuncture of a brachial vein. Blood samples were taken just before the operation, at 1,4,12 and 24 h afterwards, and then at frequent intervals until 10 weeks of age. Blood was collected in heparinized syringes and the plasma separated by centrifugation (2000 # for 15 min) and stored at -20 °C until assayed. In the second part of the experiment, 27 cockerels were hemicastrated and a further 27 were kept as intact controls. Hemicastrated animals only were starved 24 h before the operation. Blood samples were taken twice a week by venepuncture of a brachial vein up to 26 weeks of age. Body weights and comb areas (i.e. height length, Jones & Lamoreux, 1943) were recorded each week. an
Radioimmunoassay of testosterone For samples taken up to 10 weeks of age, testosterone levels were measured by radio¬ immunoassay after solvent extraction of the plasma. After 10 weeks of age, the relatively high levels of testosterone in the plasma permitted its measurement by direct radioimmuno¬ assay of the plasma samples using the method developed by Driot, Gamier & Terqui (1978).
The cross-reaction of the testosterone antiserum was 44% with 5a-dihydrotestosterone and less than 1% with either 5a-androstan-3ß,17ß-diol or A4-androstenedione. The minimum detectable hormone concentration was 100 pg/ml plasma by direct radioimmunoassay and 25 pg/ml plasma by radioimmunoassay with solvent extraction. The coefficients of variation within an assay were 3 and 7% for the direct and solvent extraction assays respectively. Between assay coefficients of variation were 9 and 4% for the direct and solvent extraction assays respectively. In all assays the plasma samples from one animal were assayed together. Data were analysed statistically by analysis of variance and covariance, and differences between means were determined by Student's i-test. RESULTS
Changes in levels of testosterone in plasma during sexual development of the cockerel The concentrations of testosterone in the plasma of intact cockerels can be divided into three phases (Fig. 1). During the first phase, which extended to 11 weeks of age, the levels were low (0-32 ± 0-06 (s.e.m.) ng/ml) and no significant fluctuations were observed. Between
12 and 22 weeks of age there was a tenfold increase in the mean concentrations of testo¬ slope of the regression line for the level of testosterone against time was 0-27. this During period, fluctuations in the mean levels were apparent and were emphasized as the age of the birds increased. For example, at 18 weeks of age, the values fluctuated within 20% of the mean plasma concentration for this age. The third (adult) phase which started at 23 weeks of age was characterized by large fluctuations about a mean value of 2-5 ng/ml plasma. The pattern of concentration of testosterone in plasma during sexual maturation in individual birds was similar to that described above except that at any given age the coefficient of variation of the mean value in the 27 birds was high (30%). sterone : the
Effect of hemicastration on the concentrations of testosterone in plasma during sexual development Short-term effects Hemicastration resulted in a marked fall in the mean preoperative concentration of testosterone from 0-50 + 0-08 to 0-15 ±0-03 ng/ml 12 h after the operation. In starved,
sham-operated animals the fall was less and reached a minimum of 0-25 ±0-06 ng/ml 12 h after the operation. Subsequently the level increased in a similar way to that seen in the hemicastrated birds. The mean concentrations of testosterone in the two groups were significantly (P
HEMICASTRATED GROWING COCKERELS F. J. M. DRIOT, M. DE REVIERS AND J. WILLIAMS I.N.R.A., Station de Recherches Avicoles, 37380 Nouzilly, France
(Received 21 April 1978) SUMMARY
Changes in the levels of testosterone in plasma were measured by radioimmunoassay in blood samples taken at frequent intervals between 2 and 26 weeks of age from entire
cockerels and cockerels hemicastrated before 2 weeks of age. In both groups the pattern of testosterone secretion could be divided into three clearly defined phases. In young birds, the levels of testosterone in plasma were low (0\m=.\3ng/ml) but in the prepubertal period, at 11 weeks of age, they started to rise and continued to rise until 22 weeks of age when adult levels, which fluctuated between 2\m=.\5and 3\m=.\5ng/ml, were reached. In the immediate period after hemicastration, the concentration of testosterone decreased temporarily. From 11 weeks of age the levels of testosterone in the hemicastrated birds were approximately 75% of those in intact birds. These results are discussed in relation to the compensatory testicular hypertrophy which occurs in growing cockerels hemicastrated at an early age. INTRODUCTION
In various species, hemicastration of the young animal induces compensatory testicular hypertrophy. This has been demonstrated in the rat (Jacobsohn & Norgren, 1965; Figarova, 1969; Liang & Liang, 1970; Hochereau de Reviers, 1975; Ojeda & Ramirez, 1972; Ramirez & Sawyer, 1974), ram (Voglmayr & Mattner, 1968; Hochereau de Reviers, 1975; Alti & Rüttle, 1976), stallion (Frerichs, 1977), field vole (Martinet & Meunier, 1975), cockerel (Benoit, 1925; Domm & Juhn, 1927), duck (Benoit, 1930) and white-crowned sparrow (Farner, Morton & Folle«, 1968). It was of interest, therefore, to compare the levels of testosterone in the plasma of intact and hemicastrated cockerels to establish the steroidogenic capability of the remaining testis in hemicastrated cockerels. MATERIALS AND METHODS
Ninety-five male birds of an egg-type strain (M 55) were purchased commercially from Station Experimentale Avicole du Magneraud (I.N.R.A., 17700 Surgeres, France), raised on the floor from the age of 1 week until 16 weeks of age and then caged singly. The light : darkness schedule was 16 h light : 8 h darkness throughout the experiment. The ambient temperature was gradually decreased from 35 to 20 °C during the first 6 weeks and then kept constant at this value. The cockerels were watered and fed ad libitum on a diet consisting of 17% protein until week 6 and 14% protein thereafter (11-7 MJ/kg). Experimental approach An examination of the changes in concentration of testosterone in plasma after hemi¬ castration of the prepubertal cockerel was carried out in two stages. The first involved
examination of the changes occurring immediately after the operation and the second entailed a long-term examination of the levels of testosterone in the plasma until sexual maturity. In both cases, hemicastration and sham-operations were performed under ether anaesthesia when the animals were 9-13 days old. In the first part of the study, all animals were starved for 24 h before the operation. Blood sampling was performed by frontal cardiac puncture up to 5 weeks of age from 15 hemicastrated, 15 sham-operated and 15 intact cockerels, and thereafter by venepuncture of a brachial vein. Blood samples were taken just before the operation, at 1,4,12 and 24 h afterwards, and then at frequent intervals until 10 weeks of age. Blood was collected in heparinized syringes and the plasma separated by centrifugation (2000 # for 15 min) and stored at -20 °C until assayed. In the second part of the experiment, 27 cockerels were hemicastrated and a further 27 were kept as intact controls. Hemicastrated animals only were starved 24 h before the operation. Blood samples were taken twice a week by venepuncture of a brachial vein up to 26 weeks of age. Body weights and comb areas (i.e. height length, Jones & Lamoreux, 1943) were recorded each week. an
Radioimmunoassay of testosterone For samples taken up to 10 weeks of age, testosterone levels were measured by radio¬ immunoassay after solvent extraction of the plasma. After 10 weeks of age, the relatively high levels of testosterone in the plasma permitted its measurement by direct radioimmuno¬ assay of the plasma samples using the method developed by Driot, Gamier & Terqui (1978).
The cross-reaction of the testosterone antiserum was 44% with 5a-dihydrotestosterone and less than 1% with either 5a-androstan-3ß,17ß-diol or A4-androstenedione. The minimum detectable hormone concentration was 100 pg/ml plasma by direct radioimmunoassay and 25 pg/ml plasma by radioimmunoassay with solvent extraction. The coefficients of variation within an assay were 3 and 7% for the direct and solvent extraction assays respectively. Between assay coefficients of variation were 9 and 4% for the direct and solvent extraction assays respectively. In all assays the plasma samples from one animal were assayed together. Data were analysed statistically by analysis of variance and covariance, and differences between means were determined by Student's i-test. RESULTS
Changes in levels of testosterone in plasma during sexual development of the cockerel The concentrations of testosterone in the plasma of intact cockerels can be divided into three phases (Fig. 1). During the first phase, which extended to 11 weeks of age, the levels were low (0-32 ± 0-06 (s.e.m.) ng/ml) and no significant fluctuations were observed. Between
12 and 22 weeks of age there was a tenfold increase in the mean concentrations of testo¬ slope of the regression line for the level of testosterone against time was 0-27. this During period, fluctuations in the mean levels were apparent and were emphasized as the age of the birds increased. For example, at 18 weeks of age, the values fluctuated within 20% of the mean plasma concentration for this age. The third (adult) phase which started at 23 weeks of age was characterized by large fluctuations about a mean value of 2-5 ng/ml plasma. The pattern of concentration of testosterone in plasma during sexual maturation in individual birds was similar to that described above except that at any given age the coefficient of variation of the mean value in the 27 birds was high (30%). sterone : the
Effect of hemicastration on the concentrations of testosterone in plasma during sexual development Short-term effects Hemicastration resulted in a marked fall in the mean preoperative concentration of testosterone from 0-50 + 0-08 to 0-15 ±0-03 ng/ml 12 h after the operation. In starved,
sham-operated animals the fall was less and reached a minimum of 0-25 ±0-06 ng/ml 12 h after the operation. Subsequently the level increased in a similar way to that seen in the hemicastrated birds. The mean concentrations of testosterone in the two groups were significantly (P
