The excretion of prostacyclin (PGI2) in milk and its possible role as a vasodilator in the mammary gland of goats

Regulation of mammary glucose uptake in goats: role of mammary gland supply, insulin, IGF-1 and synthetic capacity

“…MBV multiplied by arterial glucose concentration was used as an index (arbitrary units) of mammary glucose uptake. This was justified by findings of Christensen et al (1989) that milk vein diameter is unaffected by stage of pregnancy-lactation in multiparous goats, and changes in MBV therefore reflect changes in mammary blood flow.…”

“…Arterio-venous (AV) concentration differences for glucose across the mammary gland were used as a measure of capacity for mammary glucose uptake. Milk vein blood velocity (MBV) measured by Doppler ultrasound was used as a relative measure of mammary blood flow (Christensen et al 1989) and arterial nutrient concentration and MBV were then used as relative estimates of nutrient supply to the mammary gland. Daily milk yield and glucose concentration in milk were used as indicators of mammary metabolic activity, where glucose in milk is assumed to reflect intracellular concentrations (Kuhn & White, 1975 ;Faulkner et al 1981).…”

“…In each experimental week, MBV was measured on day 1 by the non-invasive ultrasound Doppler technique (Christensen et al 1989), then on day 2 goats were sedated for approximately 30 min with 0n2-0n3 ml Rompun (Janssen Pharma A\S, DK-3460 Birkerød, Denmark), while a 16 gauge teflon catheter (Secalon2 T, BOC Ohmeda AB) was inserted into one carotid artery and 18-gauge catheters (Venflon2 2, Ohmeda, Swindon, UK) into both milk veins. Milk-vein catheters were fitted with obturators to avoid kinking.…”

Regulation of mammary glucose uptake in goats: role of mammary gland supply, insulin, IGF-1 and synthetic capacity

“…MBV multiplied by arterial glucose concentration was used as an index (arbitrary units) of mammary glucose uptake. This was justified by findings of Christensen et al (1989) that milk vein diameter is unaffected by stage of pregnancy-lactation in multiparous goats, and changes in MBV therefore reflect changes in mammary blood flow.…”

“…Arterio-venous (AV) concentration differences for glucose across the mammary gland were used as a measure of capacity for mammary glucose uptake. Milk vein blood velocity (MBV) measured by Doppler ultrasound was used as a relative measure of mammary blood flow (Christensen et al 1989) and arterial nutrient concentration and MBV were then used as relative estimates of nutrient supply to the mammary gland. Daily milk yield and glucose concentration in milk were used as indicators of mammary metabolic activity, where glucose in milk is assumed to reflect intracellular concentrations (Kuhn & White, 1975 ;Faulkner et al 1981).…”

“…In each experimental week, MBV was measured on day 1 by the non-invasive ultrasound Doppler technique (Christensen et al 1989), then on day 2 goats were sedated for approximately 30 min with 0n2-0n3 ml Rompun (Janssen Pharma A\S, DK-3460 Birkerød, Denmark), while a 16 gauge teflon catheter (Secalon2 T, BOC Ohmeda AB) was inserted into one carotid artery and 18-gauge catheters (Venflon2 2, Ohmeda, Swindon, UK) into both milk veins. Milk-vein catheters were fitted with obturators to avoid kinking.…”

Inhibition of local blood flow control systems in the mammary glands of lactating cows affects uptakes of energy metabolites from blood

“…Although COX was shown not to be a mediator of the glucose-induced depression in IPF (Cieslar et al, 2014), depressions in IPF during COX inhibition in our study and others (Nielsen et al, 1995a;Cieslar et al, 2014) suggest a role for the vasodilator PGI 2 in the local control of MBF. For example, stimulation of mammary activity with growth hormone increases PGI 2 synthesis and MBF (Christensen et al, 1989;Nielsen et al, 2004). It is hypothesized that compounds such as CO 2 , H + , and H 2 O 2 released from the mammary epithelium during oxidative metabolism associated with a workload activate endothelial COX to produce PGI 2 and thereby support the workload with MBF (Thengchaisri and Kuo, 2003;Cieslar et al, 2014).…”

Mammary blood flow and metabolic activity are linked by a feedback mechanism involving nitric oxide synthesis

“…Furthermore, stimulation of mammary activity with growth hormone increases PGI 2 synthesis and MBF (Christensen et al, 1989;Nielsen et al, 2004), and a vasodilatory effect of CO 2 in the mammary vasculature accounts for approximately one-third of the variation in MBF throughout lactation (Nielsen et al, 1995b). In the feedforward scenario, VDC are released into the interstitium as a result of oxidative catabolism, activating PGI 2 and NO synthesis in the endothelium and causing vascular relaxation.…”

Regulation of mammary glucose uptake in goats: role of mammary gland supply, insulin, IGF-1 and synthetic capacity

“…MBV multiplied by arterial glucose concentration was used as an index (arbitrary units) of mammary glucose uptake. This was justified by findings of Christensen et al (1989) that milk vein diameter is unaffected by stage of pregnancy-lactation in multiparous goats, and changes in MBV therefore reflect changes in mammary blood flow.…”

“…Arterio-venous (AV) concentration differences for glucose across the mammary gland were used as a measure of capacity for mammary glucose uptake. Milk vein blood velocity (MBV) measured by Doppler ultrasound was used as a relative measure of mammary blood flow (Christensen et al 1989) and arterial nutrient concentration and MBV were then used as relative estimates of nutrient supply to the mammary gland. Daily milk yield and glucose concentration in milk were used as indicators of mammary metabolic activity, where glucose in milk is assumed to reflect intracellular concentrations (Kuhn & White, 1975 ;Faulkner et al 1981).…”

“…In each experimental week, MBV was measured on day 1 by the non-invasive ultrasound Doppler technique (Christensen et al 1989), then on day 2 goats were sedated for approximately 30 min with 0n2-0n3 ml Rompun (Janssen Pharma A\S, DK-3460 Birkerød, Denmark), while a 16 gauge teflon catheter (Secalon2 T, BOC Ohmeda AB) was inserted into one carotid artery and 18-gauge catheters (Venflon2 2, Ohmeda, Swindon, UK) into both milk veins. Milk-vein catheters were fitted with obturators to avoid kinking.…”

Inhibition of local blood flow control systems in the mammary glands of lactating cows affects uptakes of energy metabolites from blood

“…Although COX was shown not to be a mediator of the glucose-induced depression in IPF (Cieslar et al, 2014), depressions in IPF during COX inhibition in our study and others (Nielsen et al, 1995a;Cieslar et al, 2014) suggest a role for the vasodilator PGI 2 in the local control of MBF. For example, stimulation of mammary activity with growth hormone increases PGI 2 synthesis and MBF (Christensen et al, 1989;Nielsen et al, 2004). It is hypothesized that compounds such as CO 2 , H + , and H 2 O 2 released from the mammary epithelium during oxidative metabolism associated with a workload activate endothelial COX to produce PGI 2 and thereby support the workload with MBF (Thengchaisri and Kuo, 2003;Cieslar et al, 2014).…”

Mammary blood flow and metabolic activity are linked by a feedback mechanism involving nitric oxide synthesis

“…Furthermore, stimulation of mammary activity with growth hormone increases PGI 2 synthesis and MBF (Christensen et al, 1989;Nielsen et al, 2004), and a vasodilatory effect of CO 2 in the mammary vasculature accounts for approximately one-third of the variation in MBF throughout lactation (Nielsen et al, 1995b). In the feedforward scenario, VDC are released into the interstitium as a result of oxidative catabolism, activating PGI 2 and NO synthesis in the endothelium and causing vascular relaxation.…”

Regulation of mammary glucose uptake in goats: role of mammary gland supply, insulin, IGF-1 and synthetic capacity

“…MBV multiplied by arterial glucose concentration was used as an index (arbitrary units) of mammary glucose uptake. This was justified by findings of Christensen et al (1989) that milk vein diameter is unaffected by stage of pregnancy-lactation in multiparous goats, and changes in MBV therefore reflect changes in mammary blood flow.…”

“…Arterio-venous (AV) concentration differences for glucose across the mammary gland were used as a measure of capacity for mammary glucose uptake. Milk vein blood velocity (MBV) measured by Doppler ultrasound was used as a relative measure of mammary blood flow (Christensen et al 1989) and arterial nutrient concentration and MBV were then used as relative estimates of nutrient supply to the mammary gland. Daily milk yield and glucose concentration in milk were used as indicators of mammary metabolic activity, where glucose in milk is assumed to reflect intracellular concentrations (Kuhn & White, 1975 ;Faulkner et al 1981).…”

“…In each experimental week, MBV was measured on day 1 by the non-invasive ultrasound Doppler technique (Christensen et al 1989), then on day 2 goats were sedated for approximately 30 min with 0n2-0n3 ml Rompun (Janssen Pharma A\S, DK-3460 Birkerød, Denmark), while a 16 gauge teflon catheter (Secalon2 T, BOC Ohmeda AB) was inserted into one carotid artery and 18-gauge catheters (Venflon2 2, Ohmeda, Swindon, UK) into both milk veins. Milk-vein catheters were fitted with obturators to avoid kinking.…”

Inhibition of local blood flow control systems in the mammary glands of lactating cows affects uptakes of energy metabolites from blood

“…Although COX was shown not to be a mediator of the glucose-induced depression in IPF (Cieslar et al, 2014), depressions in IPF during COX inhibition in our study and others (Nielsen et al, 1995a;Cieslar et al, 2014) suggest a role for the vasodilator PGI 2 in the local control of MBF. For example, stimulation of mammary activity with growth hormone increases PGI 2 synthesis and MBF (Christensen et al, 1989;Nielsen et al, 2004). It is hypothesized that compounds such as CO 2 , H + , and H 2 O 2 released from the mammary epithelium during oxidative metabolism associated with a workload activate endothelial COX to produce PGI 2 and thereby support the workload with MBF (Thengchaisri and Kuo, 2003;Cieslar et al, 2014).…”

Mammary blood flow and metabolic activity are linked by a feedback mechanism involving nitric oxide synthesis

“…Furthermore, stimulation of mammary activity with growth hormone increases PGI 2 synthesis and MBF (Christensen et al, 1989;Nielsen et al, 2004), and a vasodilatory effect of CO 2 in the mammary vasculature accounts for approximately one-third of the variation in MBF throughout lactation (Nielsen et al, 1995b). In the feedforward scenario, VDC are released into the interstitium as a result of oxidative catabolism, activating PGI 2 and NO synthesis in the endothelium and causing vascular relaxation.…”