The mechanism of the inhibitory action of adrenaline on the mammary gland

β2-Adrenoceptor Activation Favor Acquisition of Tumorigenic Properties in Non-Tumorigenic MCF-10A Breast Epithelial Cells

Noradrenaline and adrenaline, and their cognate receptors, are currently accepted to participate in cancer progression. They may also participate in cancer initiation, although their role in this phase is much less explored. The aim of this work was to study the influence of adrenergic stimulation in several processes related to breast cancer carcinogenesis, using several adrenergic agonists in the MCF-10A non-tumorigenic breast cells. Activation of the β-adrenoceptors promoted an epithelial phenotype in MCF-10A cells, revealed by an increased expression of the epithelial marker E-cadherin and a decrease in the mesenchymal markers, N-cadherin and vimentin. MCF-10A cell motility and migration were also impaired after the β-adrenoceptors activation. Concomitant with this effect, β-adrenoceptors decrease cell protrusions (lamellipodia and filopodia) while increasing cell adhesion. Activation of the β-adrenoceptors also decreases MCF-10A cell proliferation. When the MCF-10A cells were cultured under low attachment conditions, activation the of β- (likely β2) or of α2-adrenoceptors had protective effects against cell death, suggesting a pro-survival role of these adrenoceptors. Overall, our results showed that, in breast cells, adrenoceptor activation (mainly through β-adrenoceptors) may be a risk factor in breast cancer by inducing some cancer hallmarks, providing a mechanistic explanation for the increase in breast cancer incidences that may be associated with conditions that cause massive adrenergic stimulation, such as stress.

Metagenomic and Metabolomic Insights Into the Mechanism Underlying the Disparity in Milk Yield of Holstein Cows

This study was conducted to investigate the metabolic mechanism underlying the disparity in the milk yield of Holstein cows. Eighteen lactating Holstein cows in their second parity and 56 (±14.81 SD) days in milking (DIM) were selected from 94 cows. Based on the milk yield of the cows, they were divided into two groups of nine cows each, the high milk yield group (HP) (44.57 ± 2.11 kg/day) and the low milk yield group (LP) (26.71 ± 0.70 kg/day). The experimental cows were fed the same diet and kept under the same management system for more than 60 days. Rumen metagenomics revealed that two Archaea genera, one Bacteria genus, eight Eukaryota genera, and two Virus genera differ between the HP and LP groups. The analysis of metabolites in the rumen fluid, milk, and serum showed that several metabolites differed between the HP and LP groups. Correlation analysis between the predominant microbiota and milk yield-associated metabolites (MP-metabolites) revealed that four Bacteria and two Eukaryota genera have a positive relationship with MP-metabolites. Pathway enrichment analysis of the differential metabolites revealed that five pathways were enriched in all the samples (two pathways in the milk, two pathways in the serum, and one pathway in the rumen fluid). Further investigation revealed that the low milk yield observed in the LP group might be due to an upregulation in dopamine levels in the rumen fluid and milk, which could inhibit the release of prolactin or suppress the action of oxytocin in the udder resulting in reduced milk yield. On the other hand, the high milk yield in the HP group is attributed to an upregulation in citrulline, and N-acetylornithine, which could be used as substrates for energy metabolism in the citric acid cycle and ultimately gluconeogenesis.

Contribution of adrenergic mechanisms for the stress-induced breast cancer carcinogenesis

Breast cancer is the most common and deadliest type of cancer in women. Stress exposure has been associated with carcinogenesis and the stress released neurotransmitters, noradrenaline and adrenaline, and their cognate receptors, can participate in the carcinogenesis process, either by regulating tumor microenvironment or by promoting systemic changes. This work intends to provide an overview of the research done in this area and try to unravel the role of adrenergic ligands in the context of breast carcinogenesis. In the initiation phase, adrenergic signaling may favor neoplastic transformation of breast epithelial cells whereas, during cancer progression, may favor the metastatic potential of breast cancer cells. Additionally, adrenergic signaling can alter the function and activity of other cells present in the tumor microenvironment towards a protumor phenotype, namely macrophages, fibroblasts, and by altering adipocyte's function. Adrenergic signaling also promotes angiogenesis and lymphangiogenesis and, systemically, may induce the formation of preneoplastic niches, cancer-associated cachexia and alterations in the immune system which contribute for the loss of quality of life of breast cancer patients and their capacity to fight cancer. Most studies points to a major contribution of β₂ -adrenoceptor activated pathways on these effects. The current knowledge of the mechanistic pathways activated by β₂ -adrenoceptors in physiology and pathophysiology, the availability of selective drugs approved for clinical use and a deeper knowledge of the basic cellular and molecular pathways by which adrenergic stimulation may influence cancer initiation and progression, opens the possibility to use new therapeutic alternatives to improve efficacy of breast cancer treatments.

Physiological mechanisms, behavioral and psychological factors influencing the transfer of milk from mothers to their young

This article is part of a Special Issue "Parental Care".Producing milk to support the growth of their young is a central element of maternal care in mammals. In spite of the facts that ecological constraints influence nursing frequency, length of time until weaning and the composition of milk, there is considerable similarity in the anatomy and physiology of milk production and delivery across mammalian species. Here we provide an overview of cross species variation in nursing patterns and milk composition as well as the mechanisms underlying mammary gland development, milk production and letdown. Not all women breastfeed their infants, thus in later sections we review studies of factors that facilitate or impede the initiation and duration of breastfeeding. The results of these investigations suggest that the decisions to initiate and maintain breastfeeding are influenced by an array of personal, social and biological factors. Finally, studies comparing the development of breastfed and formula fed infants as well as those investigating associations between breastfeeding, maternal health and mother/infant interaction are reviewed. Leading health agencies including the World Health Organization and CDC advocate breastfeeding for at least the first 6months postpartum. To achieve these rates will require not only institutional support but also a focus on individual mother/infant dyads and their experience.

Mammary blood flow regulation in the nursing rabbit

Cardiac output and mammary blood flow distribution prior to and after suckling were studied in 10 nursing rabbits by means of radionuclide-labeled microspheres. Suckling was followed by a 5.8% rise in cardiac output and a 20.4% rise in mammary blood flow. Determinations of intraglandular blood flow distribution have shown that there was a 43% increase in blood flow to the glands suckled from as compared to a 22.7% rise to the contralateral untouched glands and a 4.9% rise in the remainder of untouched glands. The conclusion is that a local mechanism may be involved in the regulation of mammary blood flow in the nursing rabbit.

Is oxytocin really necessary for efficient milk removal in dairy cows?

This review examines the potential importance of mechanisms other than the release of oxytocin for efficient milk removal. First, evidence is presented that oxytocin release is not always essential for efficient milk removal. Second, potential roles for the release of oxytocin during suckling or milking not directly related to milk removal are discussed. Third, alternative mechanisms that potentiate or induce milk ejection are introduced. Finally, the role of the autonomic nervous system in the milk removal process is examined.

Influence of herd relocation upon production and endocrine traits of dairy cows

Effects of potential stress encountered by two Holstein herds relocated into a new double-six herringbone parlor and free-stall facility were studied by evaluating alterations of milk yield and fat percentage, mastitis status, corticosteroids, and heat detection. One-half of one herd (18 cows) was moved 100 m to new facilities (Merged), and the remaining 18 cows were maintained in their original tie-stall barn (Control). The same day, the second herd of 50 cows (Moved) was transported via stock trailer 7 km to new facilities. Milk yield by Merged and Moved cows was decreased at first milking, but subsequent milk yields were similar to yields prerelocation. Milk fat percentage was decreased for only 3 days for Moved cows but was unchanged for Merged cows. Across groups, older cows and cows in late lactation tended to have greatest decreases in milk yield. Corticosteroids in serum were increased in Merged cows for only 2 days after relocation. No changes in milk somatic cell count or percentage heats detected were associated with relocation. Detrimental effects of herd relocation were slight and indicate that dairy herds can be moved without adversely affecting production traits.

Effect of teat stimulation on sympathetic tone in bovine mammary gland

Rate of contraction of teat sphincter muscle in cows is partially under sympathetic control. To investigate the effect of teat stimulation on sympathetic tone in the mammary gland, rates of spontaneous rhythmic contractions of teat sphincter muscle were measured prior to and during eight machine milkings by pressure transponding devices. Transponding devices were inserted into right front and right rear teat ducts. After a 5-min control, the udder was prepped for 1.5-min, the right front transponder was removed, and then the left front, left rear, and right front quarters were milked while contractile frequency of the right rear sphincter muscle continued to be monitored. During the control period, teat sphincter muscles contracted with a nominal frequency of from two to four per min. Rhythmic contraction of the teat sphincter muscle decreased by about one per min during manual stimulation of the udder. Toward the end of milking, rates reached a low, and in half of the trials there were no contractions. After milking, with teats no longer stimulated, contractile frequency rose towards baseline in the unmilked right rear quarters. This decrease in rate of contraction is likely from a decrease in sympathetic tone in the mammary gland resulting from an autonomic reflex to teat stimulation.

Endocrine responses of cows subjected to controlled voltages during milking

For the relative influence of central and of peripheral inhibitive mechanisms on the milk-ejection reflex, dairy cows were subjected to control voltages during milking. Integrated 1-min jugular vein samples were taken at -20, -12, -9, -2, -1, 2, 4, 6, 10, and 20 min relative to the start of milking for measurement of norepinephrine, epinephrine, dopamine, oxytocin, and prolactin. Cows were subjected to voltages that resulted in body currents of 5 mA. For the response of cows to continuously applied voltage, the voltage remained on for 20 min starting 10 min prior to milking. For the response to intermittently applied voltage, the voltage was on for 5 of every 30 s. Milk yield and milking time were decreased in cows subjected to stimulation by intermittent voltage. This decrease could not be explained by changes in peripheral concentrations of either oxytocin or catecholamines. Plasma prolactin did decrease; however, it seems unlikely the prolactin would affect the milk-ejection reflex. We hypothesize that this decrease in milk yield resulted from neural mediated changes within the mammary gland.

Inhibitory effect of adrenaline on oxytocin release in the ewe during the milk-ejection reflex

Milk-ejection activity was determined in the blood plasma of ewes during normal milking and during milking when adrenaline was injected intravenously before or after udder stimulation. It was found that administration of adrenaline either before or after udder washing, decreased the oxytocin concentration and milk yield but increased the yield by hand-stripping. Adrenaline also retards the average time for peak oxytocin concentration. These results and the use of a beta-receptor blocker to inhibit the effect of adrenaline at the myoepithelial cell level indicate that in ewes adrenaline can prevent the release of oxytocin from neurohypophysis.

Vasopressin release by nicotine: the site of action

1. In cats anaesthetized with chloralose the release of neurohypophysial hormones was examined after injection of nicotine into the cerebral ventricles or cisterna magna or its topical application through perspex rings to the ventral surface of the brain stem. The release was measured by assaying the hormones in samples of venous blood. 2. Injected into a lateral or the third cerebral ventricle, nicotine (0.5 to 1 mg) produced release of vasopressin without oxytocin. When the aqueduct was cannulated, preventing access to the fourth ventricle and to the subarachnoid space, this release did not occur. 3. Vasopressin was also released without oxytocin when nicotine (0.25 to 2 mg) was injected into the subarachnoid space through the cisterna magna. With this route of administration the nicotine did not enter any part of the ventricular system. 4. Applied through paired perspex rings placed across the ventral surface of the brain stem, nicotine again produced release of vasopressin without ocytocin. The amount of nicotine placed in each ring was usually 80 mug, but a release was obtained with 10 mug and in one experiment with as little as 5 mug. 5. The bilateral region on the ventral surface of the brain stem where nicotine acts when producing release of vasopressin lies lateral to the pyramids and in a longitudinal direction, 6 to 9 mm caudal to the trapezoid bodies. 6. The vasopressin release by nicotine injected intraventricularly or intracisternally, or applied topically to the ventral surface of the brain stem was not due to absorption of nicotine into the blood stream, nor to blood pressure effects. 7. It is concluded that nicotine acts on the ventral surface of the brain stem probably by activating the central projection to the supra-optic and possibly also the paraventricular nuclei of afferent pathways in the sinus and vagus nerves which control the release of vasopressin in response to changes in blood volume or distribution.

The hypothalamic neurosecretory pathways for the release of oxytocin and vasopressin in the cat

1. The neurones of the supraoptic nucleus (SON) and paraventricular nucleus (PVN) were stimulated electrically in lactating cats under chloralose anaesthesia. Milk-ejection responses were used to monitor the release of oxytocin and vasopressin and both hormones were assayed in samples of blood collected during stimulation. The position of the tip of the stimulating electrode was confirmed from brain sections stained selectively for cystine-rich neurosecretory material.2. A previous finding that stimulation of the SON in the cat releases vasopressin without oxytocin was confirmed.3. Stimulation of the PVN caused both hormones to be released. The ratio of their concentrations in blood was variable; this suggests release from separate neurones.4. Both hormones were also released on stimulation of the median eminence but not of the zone lying vertically between this structure and the PVN. No neurosecretory material was detected in this zone. These findings argue against the existence of a direct or medial paraventriculo-hypophysial pathway running downwards along the wall of the third ventricle.5. Study of sections from unstimulated brains confirmed that the tractus paraventricularis cinereus of Greving which runs ventro-laterally from the PVN towards the SON, represents the principal efferent pathway for neurosecretory fibres from the PVN.6. The results are discussed in relation to the problem of the independent release of oxytocin and vasopressin in response to physiological stimulation of the neurohypophysis.

A sensitive and specific assay for vasopressin in the circulating blood

1. A search was made for an assay tissue with selective sensitivity to vasopressin. Of those smooth muscle preparations tested, the longitudinal muscle of the isolated rectum of the rabbit was the most satisfactory.2. The rabbit isolated rectum, bathed in Krebs solution, was contracted by acetylcholine, angiotensin II amide, bradykinin and 5-hydroxytryptamine. It was relaxed by vasopressin, oxytocin and the catecholamines.3. Vasopressin was active in concentrations of 4-100 muu./ml (0.01-0.25 ng/ml) and was 20-30 times more active than oxytocin. Bretylium had no effect on the relaxant action of vasopressin; nor did concentrations of alpha- and beta-adrenoceptor blocking agents sufficient to abolish the actions of catecholamines. Lignocaine reduced the sensitivity of the rabbit rectum to both vasopressin and oxytocin without altering the actions of adrenaline. High concentrations of either vasopressin or oxytocin desensitized the rabbit rectum to the actions of both hormones, without affecting the actions of adrenaline. It was concluded that vasopressin and oxytocin act on a common population of receptors different from those for catecholamines.4. Phentolamine, unlike other alpha-adrenoceptor antagonists, reduced the relaxant action of vasopressin on the rectum.5. When superfused with blood from an anaesthetized dog, the rabbit rectum maintained a higher tone than in Krebs solution; it retained its sensitivity to vasopressin. Pronethalol, administered intraluminally, reduced spontaneous movement and abolished the actions of low concentrations of catecholamines, thereby increasing the specificity of the assay. No other substance tested relaxed the rectum in concentrations likely to be found in blood.6. Vasopressin was stable in dog's blood; it survived passage through the pulmonary vascular bed; it had a half-life in the circulation of about 1 min.7. The half-life of vasopressin in the circulation may depend upon the duration of the infusion.

Blood levels of oxytocin and vasopressin during suckling in the rabbit and the problem of their independent release

1. Oxytocin and vasopressin were assayed in samples of blood collected from conscious rabbits during suckling. The milk yields were determined from the weight gain of the litters.2. With normal milk yields (35-155 g), relatively high concentrations (31-375 muu./ml.) of oxytocin were present in the blood but vasopressin was detected in only one out of eight samples. It is concluded that the release of oxytocin by the milk-ejection reflex is essential for normal milk removal in the rabbit and that this hormone is released independently of vasopressin.3. When the milk yield did not exceed 15 g, an amount which could be removed by passive withdrawal from the mammary gland, vasopressin was detected in four out of five blood samples but none contained a detectable concentration of oxytocin. This result can be explained by the intervention of emotional stress which is known to block the milk-ejection reflex but which acts as a stimulus for the release of vasopressin.4. Emotional stress could inhibit the milk-ejection reflex either centrally by blocking the release of oxytocin, or peripherally by blocking the response of the mammary gland to circulating oxytocin. The absence of the hormone in blood during ineffectual suckling suggests that the block is central.

The pharmacology of salivary myoepithelial cells in dogs

1. Pressure changes in the submaxillary and parotid ducts of dogs, induced by nerve stimulation or intravenous injection of drugs, were studied.2. Pressure rises could be elicited by parasympathetic stimulation and by acetylcholine and methacholine, even when no secretion was evoked. These effects were abolished by atropine.3. Similarly, sympathetic stimulation, adrenaline, noradrenaline and phenylephrine raised the pressure in both glands, also in the absence of secretion. Dihydroergotamine abolished these effects. Isoprenaline increased the pressure in the submaxillary duct, but only when it caused secretion. This effect was abolished by propranolol. In the parotid gland isoprenaline caused neither secretion nor pressure rise. It is concluded that the myoepithelial cells of the two glands are supplied with alpha-adrenoceptors.4. Doses of histamine, bradykinin, kallidin and physalaemin which caused no salivary secretion raised the duct pressure even when dihydroergotamine, propranolol and atropine had been given.5. Angiotensin and 5-hydroxytryptamine increased the pressure only in some experiments. Oxytocin caused very little or no pressure rise. Vasopressin had no effect of its own but reduced the pressure raising effects of nerve stimulation or drugs.